reactions questions

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GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 1

Look at the following section of the periodic table.
1

2

3

4

5

66

7

0
He

H
Li

Be

B

C

N

O

F

Ne

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

Ga

Ge

As

Se

Br

Kr

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Use only the elements shown to answer the following questions.

When metals react with non-metals they form ionic compounds.

(i)

How do metal atoms form ions?

e.c

(a)

Zn

om

Sc

......................................................................................................................................................................... [1]

ctiv

(ii) Write the symbol of a metal that forms +1 ions.

......................................................................................................................................................................... [1]

(i)

Write down the formulae of:
an aluminium ion.

ma

(b)

(ii) a chloride ion.

he

......................................................................................................................................................................... [1]

......................................................................................................................................................................... [1]

ww
w.c

(iii) aluminium chloride.

......................................................................................................................................................................... [1]
(c)

When non-metals react with non-metals they form molecules.

(i)

What type of bonding is found in molecules?

......................................................................................................................................................................... [1]
(ii) Tetrachlormethane is a compound of carbon and chlorine. Write down the formula of tetrachloromethane.
......................................................................................................................................................................... [1]

(iii) Ammonia exists as molecules.
Draw a dot and cross diagram to show the bonding in ammonia.

[2]
TOTAL / 9

GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 2

When calcium carbonate (limestone) is heated it produces calcium oxide and carbon dioxide.
(i)

Complete the following equation
CaCO3

→

CaO

+

________

[1]

(ii) What name is given to this type of reaction?
......................................................................................................................................................................... [1]
Calculate the relative molecular mass of calcium carbonate.
(relative atomic masses: C=12, O=16, Ca=40)

om

(b)(i)

......................................................................................................................................................................... [1]

e.c

(ii) How many tonnes of calcium carbonate are needed to produce 280 tonnes of calcium oxide?
..............................................................................................................................................................................

ctiv

..............................................................................................................................................................................
..............................................................................................................................................................................

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w.c

he

ma

......................................................................................................................................................................... [3]

TOTAL / 6

GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 3

(a)

When magnesium burns in oxygen it produces magnesium oxide.
Balance the following symbol equation.
__Mg(s)

+

O2(g)

→

__MgO(s)

[1]

om

(b) Alison carefully reacted some magnesium with oxygen using the equipment below.
She made sure that all the magnesium had reacted.
tongs

e.c

lid

heat

ma

Here are the results of Alison’s experiment.

ctiv

crucible
coil of magnesium
ribbon
pipeclay triangle

= 40.1 g
= 44.9 g
= 48.1 g

he

mass of crucible + lid
mass of crucible + lid + magnesium
mass of crucible + lid + magnesium oxide

ww
w.c

Use Alison’s results to calculate the empirical formula of magnesium oxide.
(relative atomic masses: O = 16, Mg = 24)
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
......................................................................................................................................................................... [6]

TOTAL / 7

GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 4

The diagram shows an experiment to investigate the effect of heat on copper(II) sulphate crystals.

heat

tube A

blue copper(ll)
sulphate crystals

tube B

om

cold water

(a)(i)

e.c

colourless liquid

Why is cold water used in the beaker?

ctiv

......................................................................................................................................................................... [1]
(ii) How could you identify the colourless liquid in tube B as water?
..............................................................................................................................................................................

(b)

ma

......................................................................................................................................................................... [1]
When 2.5 g of blue copper(II) sulphate crystals were heated, 1.6 g of white solid were left in tube A.
Calculate the mass of water driven off in the experiment.

he

(i)

......................................................................................................................................................................... [1]

ww
w.c

(ii) Calculate the percentage of water driven off.

..............................................................................................................................................................................
......................................................................................................................................................................... [2]
(c)

The equation represents the change taking place on heating blue copper(II) sulphate crystals.
CuSO4.5H2O ∏

CuSO4

+

5H2O

(i) What type of change is taking place?
......................................................................................................................................................................... [1]

(ii) Write an equation to represent what happens when water is added to white copper(II) sulphate.
......................................................................................................................................................................... [1]
(ii) What symbol should be used instead of the arrow in the first equation?
......................................................................................................................................................................... [1]
TOTAL / 8

GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 5

Nitrogen is an important element to help plants to grow.
Artificial fertilisers contain compounds of nitrogen.
Two such compounds are sodium nitrate (NaNO3), ammonium nitrate (NH4NO3).
(a)

Calculate the relative molecular masses of each of these compounds.
(Relative atomic masses: H = 1, C = 12, N = 14, O = 16, Na = 23)

(i)

sodium nitrate.

om

..............................................................................................................................................................................

......................................................................................................................................................................... [2]
(ii) ammonium nitrate.

..............................................................................................................................................................................
..............................................................................................................................................................................
......................................................................................................................................................................... [2]
(c)

Which of them would be best for a farmer to use?
......................................................................................................................................................................... [1]

(d)

Ammonia, NH3 has 82.4% of nitrogen in it.
Give two reasons why it would be unsuitable for use as a fertiliser.

..............................................................................................................................................................................
......................................................................................................................................................................... [2]
TOTAL / 9

GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 6

(a)

Calculate the empirical formulae of the following compounds.
(Relative atomic masses: H=1, C=12, N=14, O=16, S=32, K=39, Fe=56)

(i)

a compound of 3.5 g nitrogen and 4 g oxygen.

..............................................................................................................................................................................
..............................................................................................................................................................................

om

......................................................................................................................................................................... [2]
(ii) a compound of 50% oxygen and 50% sulphur.

e.c

..............................................................................................................................................................................
..............................................................................................................................................................................

ctiv

......................................................................................................................................................................... [2]
(iii) a compound of 39% potassium, 1% hydrogen, 12% carbon and 48% oxygen.
..............................................................................................................................................................................

ma

..............................................................................................................................................................................
......................................................................................................................................................................... [2]

he

(iv) 16.0 g of an oxide of iron formed from 11.2 g iron.

..............................................................................................................................................................................

ww
w.c

..............................................................................................................................................................................
......................................................................................................................................................................... [3]
(b)

Find (i) the empirical formula and (ii) the molecular formula of a compound containing
4.04% hydrogen, 24.24% carbon and 71.72% chlorine, given the following information:
relative atomic masses: H=1, C=12, Cl=35.5
relative molecular mass of the compound = 99
(i)
..............................................................................................................................................................................
..............................................................................................................................................................................
......................................................................................................................................................................... [3]
(ii)
..............................................................................................................................................................................
......................................................................................................................................................................... [2]
TOTAL / 14

GCSE CHEMISTRY

REACTIONS & FORMULAE

High Demand Questions

QUESTIONSHEET 7

A chemist finds a compound in an unlabelled bottle.
He carries out a number of experiments on it.
Here are his results.
colour
heat
add dilute hydrochloric acid
heat and pass hydrogen over it
Identify the black solid.

om

(a)

black
no change
solution of green salt
brown solid, gas which condenses to colourless liquid

......................................................................................................................................................................... [1]
Identify the green salt.

e.c

(b)(i)

......................................................................................................................................................................... [1]

ctiv

(ii) What products would be formed when a solution of the green salt is electrolysed?
..............................................................................................................................................................................
......................................................................................................................................................................... [2]

ma

(iii) How can the gas produced during electrolysis be identified by a chemical test?
..............................................................................................................................................................................

(c)(i)

he

......................................................................................................................................................................... [2]
Name the brown solid produced in the fourth test.

ww
w.c

......................................................................................................................................................................... [1]
(ii) Name the liquid which condenses in the fourth test.
......................................................................................................................................................................... [1]
(iii) Write an equation for the reaction.

......................................................................................................................................................................... [1]
(ii) Calculate the mass of BaCl2.xH2O.

e.c

......................................................................................................................................................................... [1]
(iii) Calculate the mass of BaCl2 after heating.
......................................................................................................................................................................... [1]
(iv) Calculate the mass of water lost.

ctiv

......................................................................................................................................................................... [1]
(v) Calculate the percentage of water in the BaCl2.xH2O.
..............................................................................................................................................................................

(b)

ma

......................................................................................................................................................................... [2]
What could be done to ensure that all the water had been lost?

he

..............................................................................................................................................................................
..............................................................................................................................................................................

(c)

ww
w.c

......................................................................................................................................................................... [3]
Calculate the relative molecular masses of:
(i) BaCl2
..............................................................................................................................................................................
......................................................................................................................................................................... [1]
(ii) H2O
..............................................................................................................................................................................
......................................................................................................................................................................... [1]
(Relative atomic masses: H = 1, O = 16, Cl = 35.5, Ba = 137)
(d)

Use your previous answers to determine the value of x in BaCl2.xH2O.
..............................................................................................................................................................................
..............................................................................................................................................................................
..............................................................................................................................................................................
......................................................................................................................................................................... [3]
TOTAL / 14

GCSE CHEMISTRY

REACTIONS & FORMULAE
QUESTIONSHEET 9

Medium Demand Questions

The following words describe ten different types of chemical reaction.

decomposition

precipitation

combustion

oxidation

reduction

reversible

exothermic

endothermic

displacement

neutralisation

om

Write the correct word after each of the following descriptions of chemical reactions.
(a) two solutions are mixed together and form an insoluble product

e.c

......................................................................................................................................................................... [1]

(b) a reaction in which oxygen is removed from one of the reactants

ctiv

......................................................................................................................................................................... [1]
(c) a reaction which takes in heat from the surroundings

......................................................................................................................................................................... [1]

ma

(d) a reaction where products can form the original reactants

......................................................................................................................................................................... [1]

he

(e) a single substance breaks down into two or more simpler ones
......................................................................................................................................................................... [1]
a substance loses electrons

ww
w.c

(f)

......................................................................................................................................................................... [1]
(g) one element takes the place of another in a compound
......................................................................................................................................................................... [1]
(h) a substance burns in oxygen

......................................................................................................................................................................... [1]

TOTAL / 8

GCSE CHEMISTRY

Medium Demand Questions

REACTIONS & FORMULAE
QUESTIONSHEET 10

When calcium oxide reacts with water it forms calcium hydroxide (slaked lime).
The reaction is exothermic.
(a) Explain what is meant by an ‘exothermic reaction’.
......................................................................................................................................................................... [1]

om

(b) The formula for a calcium ion is Ca2+ and that of a hydroxide ion is OH-.
Write down the formula for calcium hydroxide.
......................................................................................................................................................................... [1]
(c) Write down one use of slaked lime.

e.c

......................................................................................................................................................................... [1]

ctiv

(d) When slaked lime is dissolved in water, it produces a solution known as limewater.
It is possible to make a small amount of calcium carbonate from limewater.
Explain how this can be done.
......................................................................................................................................................................... [1]

ma

(e) How can calcium carbonate be converted into quicklime?

......................................................................................................................................................................... [1]

he

(f) The reactions described above are often put together in a diagram called the calcium cycle.
Explain the word “cycle” in this context.
..............................................................................................................................................................................

ww
w.c

......................................................................................................................................................................... [2]

TOTAL / 7

GCSE CHEMISTRY

REACTIONS & FORMULAE
QUESTIONSHEET 11

Medium Demand Questions

Solutions of different halogens were mixed with solutions of halide salts. The mixtures were shaken with some
organic solvent. Halogens dissolve better in the solvent than in water and give distinctive colours.
(chlorine - green, bromine - orange, iodine - violet)
Here are the results of some experiments.
halogen added

halide salt

A
B
C
D
E
F

chlorine
chlorine
bromine
bromine
iodine
iodine

potassium bromide
potassium iodide
potassium chloride
potassium iodide
potassium chloride

potassium bromide

colour after
shaking
orange
violet
orange
violet
violet
violet

e.c

om

experiment

ctiv

(a) What type of reaction is taking place?

......................................................................................................................................................................... [1]
(b) In which experiments are no reactions taking place?

ma

......................................................................................................................................................................... [3]
(c) Write a word equation for experiment A.

he

......................................................................................................................................................................... [1]

Write a symbol equation for experiment A.

[2]

(e)

What do the experiments tell you about the relative reactivities of chlorine, bromine and iodide?

ww
w.c

(d)

..............................................................................................................................................................................
......................................................................................................................................................................... [1]
(f)

How would you expect fluorine to react with potassium chloride?

......................................................................................................................................................................... [1]
(g) How would you expect chlorine to react with potassium fluoride?
......................................................................................................................................................................... [1]

TOTAL / 10

GCSE CHEMISTRY

REACTIONS & FORMULAE

Medium Demand Questions

QUESTIONSHEET 12

The table below gives information about the solubilities of a number of salts.
sodium
soluble
soluble

potassium
soluble
soluble

lead
insoluble
insoluble

barium
soluble
insoluble

nitrate
carbonate

soluble
soluble

soluble
soluble

soluble
insoluble

soluble
insoluble

calcium
soluble
slightly
soluble
soluble
insoluble

om

chloride
sulphate

(a)

What can you say about the solubility of sodium and potassium salts?

(b)

What can you say about the solubility of nitrates?

e.c

......................................................................................................................................................................... [1]
(iii) barium chloride solution with sodium sulphate solution
..............................................................................................................................................................................
......................................................................................................................................................................... [2]
(e)

Barium salts are poisonous, yet some X-ray patients have to drink barium sulphate.
Explain why they can do this without harming themselves.
..............................................................................................................................................................................
..............................................................................................................................................................................
......................................................................................................................................................................... [2]

TOTAL / 11

GCSE CHEMISTRY

REACTIONS & FORMULAE
QUESTIONSHEET 13

Medium Demand Questions

Five students wanted to find out what would happen when a certain compound was heated.
They found that a gas was given off, so they measured the mass of the gas lost.
Their results are shown below.
student
loss in mass (g)
volume of gas (cm3)

1

0.032
24

2
0.06
45

3
0.083
62

5
0.107
80

[4]

ctiv
ma
he
ww
w.c

loss in mass (g)

e.c

om

(a) Plot the results on the graph.

4
0.09
75

volume of gas (cm3)

(Continued...)

GCSE CHEMISTRY

REACTIONS & FORMULAE
QUESTIONSHEET 13 CONTINUED

(b)

Which student’s result is incorrect?
......................................................................................................................................................................... [1]

(c)

Use your graph to estimate:
(i)

the volume of 0.05 g of the gas.

......................................................................................................................................................................... [1]

The gas given off is oxygen.

(i)

[1]

How can the results of the experiment be used to confirm this?

e.c

(d)

the mass of 15 cm3 of the gas.

om

(ii)

..............................................................................................................................................................................

ctiv

......................................................................................................................................................................... [2]
(ii) Describe a chemical test that can confirm the identity of the gas.

ma

..............................................................................................................................................................................

ww
w.c

he

......................................................................................................................................................................... [2]

TOTAL / 11

GCSE CHEMISTRY

REACTIONS & FORMULAE
QUESTIONSHEET 14

Medium Demand Questions
Study the diagram below.
tube
A

tube
B

tube
D

tube
C

om

oil

cotton wool

(a) (i)

boiled and
cooled water

In which two tubes will the steel go rusty?

calcium
chloride

e.c

distilled
water

salt
solution

ctiv

......................................................................................................................................................................... [1]
(ii) Why does the steel not rust in the other two tubes?

ma

..............................................................................................................................................................................
......................................................................................................................................................................... [2]
In which tube will the rusting occur fastest?

Explain your answer.

he

(b)

..............................................................................................................................................................................

ww
w.c

......................................................................................................................................................................... [2]

(c)

Explain how ships and piers are prevented from rusting.
..............................................................................................................................................................................
......................................................................................................................................................................... [3]

(d)

State how each of the following is prevented from rusting.
(i)

cutlery

......................................................................................................................................................................... [1]
(ii) car bodies
......................................................................................................................................................................... [1]

TOTAL / 10

GCSE CHEMISTRY

Medium Demand Questions

REACTIONS & FORMULAE
QUESTIONSHEET 15

Zinc metal can be extracted from the mineral zinc blende (zinc sulphide)
Stage 1 - zinc blende heated in air to produce zinc oxide.
Stage 2 - zinc oxide reacted with sulphuric acid to make a solution containing zinc ions.
Stage 3 - zinc metal is obtained by electrolysis of the solution.
The zinc extracted is used to coat other metals and in alloys.
(a)

Suggest two advantages of alloys over pure metals.

om

..............................................................................................................................................................................
......................................................................................................................................................................... [2]
Name the metal that zinc is often used to protect.

e.c

(b) (i)

......................................................................................................................................................................... [1]

ctiv

(ii) What is the process of covering a metal with zinc called?

......................................................................................................................................................................... [1]
(c) (i)

Apart from zinc oxide, what other product is formed when zinc blende is heated in air?

ma

......................................................................................................................................................................... [1]

he

(ii) The formula of zinc oxide is ZnO.
The formula of an oxide ion is O2 .
What is the formula of a zinc ion?

......................................................................................................................................................................... [1]
What type of reaction occurs when zinc oxide reacts with sulphuric acid?

ww
w.c

(d)

......................................................................................................................................................................... [1]
(e)

Zinc can also be extracted from zinc oxide by heating it with coke.
(i)

What is the main element in coke?

......................................................................................................................................................................... [1]
(ii) Write an equation for the reaction between zinc oxide and coke.
......................................................................................................................................................................... [1]
(iii) What type of reaction involves the removal of oxygen?
......................................................................................................................................................................... [1]

TOTAL / 10

GCSE CHEMISTRY

REACTIONS & FORMULAE
QUESTIONSHEET 16

Medium Demand Questions

The key below is used to identify five carbonates and a hydrogencarbonate.
Does it dissolve
in water?

No

Yes
Does it give off

carbon dioxide
when heated?

Is it green?
Yes
No
sodium
carbonate

Yes

No

copper
carbonate

ammonium
carbonate

No
sodium
hydrogencarbonate

magnesium
carbonate

Yes

calcium
carbonate

Which soluble compound gives off carbon dioxide, but gives no smell?

ctiv

(a) (i)

No

e.c

Yes

om

Does it give a
red flame test?

Does it smell of
ammonia when
heated?

......................................................................................................................................................................... [1]
(ii) What type of substance will react with any carbonate or hydrogencarbonate to produce carbon dioxide?

ma

......................................................................................................................................................................... [1]
(iii) Only one carbonate in the key produces no carbon dioxide when heated.
Which one?

Tablets for upset stomachs often contain citric acid and magnesium carbonate.
Describe and explain what happens when these tablets are added to water.

ww
w.c

(b)

he

......................................................................................................................................................................... [1]

..............................................................................................................................................................................
......................................................................................................................................................................... [2]
(c)

A teaspoon of sodium hydrogencarbonate is added when making gingerbread.
(i) What is the purpose of the sodium hydrogencarbonate?
..............................................................................................................................................................................
......................................................................................................................................................................... [2]
(ii) Why would sodium carbonate be unsuitable for this purpose?
......................................................................................................................................................................... [1]

TOTAL / 8

GCSE CHEMISTRY

REACTIONS & FORMULAE

Low Demand Questions

QUESTIONSHEET 17

Quicklime, CaO, is made by heating limestone, CaCO3, in a rotating kiln.
Limestone is added at the top of the kiln. Turning the kiln lets the limestone move slowly to the bottom as it is
heated. Quicklime is formed and is taken from the bottom.
(a)

Give the chemical name for:
(i)

quicklime

om

......................................................................................................................................................................... [1]
(ii) limestone

(b)

e.c

......................................................................................................................................................................... [1]
Heat is required for the reaction to take place.
What name is given to reactions which take in heat?

(c)

ctiv

......................................................................................................................................................................... [1]
James investigated this reaction. He heated a piece of limestone on the edge of a gauze.
Describe what he saw.

ma

..............................................................................................................................................................................
..............................................................................................................................................................................

Before the rotating kiln was invented, each batch of limestone had to be heated separately.
Suggest one advantage that the rotating kiln has over the older method.

ww
w.c

(d)

he

......................................................................................................................................................................... [2]

..............................................................................................................................................................................
......................................................................................................................................................................... [1]
(e)

There are proposals to extend a limestone quarry.
(i) Give two arguments that the quarry owners could use in favour of the proposed extension.
..............................................................................................................................................................................

[3]

What result would they see if the gas was carbon dioxide?

ctiv

(ii)

e.c

sea shells

......................................................................................................................................................................... [2]

substance
sodium chloride
potassium chloride
calcium chloride
copper chloride

colour of flame
yellow
pink
red
green

Why is copper wire not used for the test?

ww

w.c

(i)

ma

They then heated a small piece of shell in a flame.
Different substances give different colours when put in a flame.

he

(b)

......................................................................................................................................................................... [1]
(ii) How is the test wire cleaned between each test?
......................................................................................................................................................................... [1]
The shells turned the flame a red colour.
(iii) Which metal is in the seashells?
......................................................................................................................................................................... [1]
(c)

Use the results of the two tests to select the chemical name of the substance from which seashells are
made from the list below.
sodium chloride

sodium carbonate

calcium carbonate

calcium chloride

......................................................................................................................................................................... [1]

TOTAL / 9

GCSE CHEMISTRY

REACTIONS & FORMULAE

Low Demand Questions

QUESTIONSHEET 19

A

B

Ethanol
C2H5OH

Kalium hydrogen
sulfat
KHSO4

D

C

Which bottle contains a potassium compound?

ma

(a)

e.c

Phosphorsaure
H3PO4

ctiv

Zinc
Zn

om

Some bottles of chemicals were imported from Germany.
Their labels are in German.

......................................................................................................................................................................... [1]
(b) (i)

Which bottle contains an element?

he

......................................................................................................................................................................... [1]

ww

w.c

(ii) What gas is formed when this element is added to dilute sulphuric acid?
......................................................................................................................................................................... [1]
(c)

Which bottle contains a flammable substance?
......................................................................................................................................................................... [1]

(d)(i) Which bottle contains a compound of four elements?
......................................................................................................................................................................... [1]
(ii) What does the hazard label on this bottle mean?
......................................................................................................................................................................... [1]
(e)

The gas, hydrogen, is known in German as “Wasserstoff”.
Wasser means water.
Suggest an explanation for the name.
..............................................................................................................................................................................
......................................................................................................................................................................... [2]
TOTAL / 8

GCSE CHEMISTRY

REACTIONS & FORMULAE

Low Demand Questions

QUESTIONSHEET 20

(a)

The diagram shows a cross section through a type of blast furnace, which was used in the Iron Age.

IRON +CHARCOAL

om

CHARCOAL

IRON
FORMED
HERE

e.c

AIR BLASTED HERE

(i)

ctiv

CLAY

The charcoal is the fuel for the furnace. Charcoal is mainly carbon.
Write an equation for the burning of charcoal in a plentiful supply of air.

ma

......................................................................................................................................................................... [1]
(ii) Some carbon monoxide may also be formed.
Why is this undesirable?

The iron ore is reduced to iron when the furnace gets hot enough.
(i)

What is meant by ‘reduced’ in this reaction?

ww
w.c

(b)

he

......................................................................................................................................................................... [1]

......................................................................................................................................................................... [1]
(ii) Name a substance that is oxidised in the process.
......................................................................................................................................................................... [1]
(c)

When the furnace was opened, the clay had changed.
List three of the changes to the clay.
..............................................................................................................................................................................
..............................................................................................................................................................................
......................................................................................................................................................................... [3]

TOTAL / 7

GCSE CHEMISTRY

REACTIONS & FORMULAE
ANSWERS AND MARK SCHEMES

QUESTIONSHEET 1
1

(ii)

Li/Na/K/Cu

1

(i)

Al3+

1

(ii)

Cl

(iii)

AlCl3

(i)

covalent

(ii)

CCl4

1

om

1

xx
H

x•

(iii)

-

N
x•
H

H

e.c

(c)

lose one or more electrons

(1 for bond pairs, 1 for lone pair)

ctiv

(b)

(i)

x•

(a)

QUESTIONSHEET 2

(ii)

thermal decomposition

(i)

100

(ii)

Mr of CaO = 56

56 t CaO produced from 100 t calcium carbonate
280 t CaO produced from 500 t calcium carbonate

ma

CO2

he

(b)

(i)

ww
w.c

(a)

1
1

2

TOTAL 9

1
1
1
1
1

1

TOTAL 6

QUESTIONSHEET 3
(a)

2 and 2

(b)

mass of magnesium = 44.9 - 40.1 = 4.8 g
mass of magnesium oxide = 48.1 - 40.1 = 8.0 g
so, mass of oxygen = 8.0 - 4.8 = 3.2 g
moles of oxygen = 3.2/16 = 0.2
moles of magnesium = 4.8/24 = 0.2
ratio Mg:O = 1:1 therefore MgO

1
1
1
1
1
1
1

TOTAL 7

GCSE CHEMISTRY

REACTIONS & FORMULAE
ANSWERS AND MARK SCHEMES

QUESTIONSHEET 4
(a)

(i)

to condense water

1

(ii)

find boiling point/boiling point is 100oC/
find freezing point/freezing point is 0oC/
blue cobalt chloride paper goes pink

1

Note: Cobalt chloride paper test only shows the presence of water, not that the substance is water.
It could be dilute acid, salt solution etc.
2.5 - 1.6 = 0.9 g

(ii)

0.9 / 2.5
= 36%

(i)

dehydration

(ii)

CuSO4 + 5H2O

1

om

(c)

(i)

∏ CuSO4.5H2O

QUESTIONSHEET 5

1
1
1
1
1

TOTAL 8

23 + 14 + (3 × 16) = 85

(ii)

14 + (4 × 1) + 14 + (3 × 16) = 80

(i)

14/85 × 100
= 16.5%

(ii)

28/80 × 100
= 35%

1
1

(c)

ammonium nitrate

1

(d)

Two from:
alkaline/gas/poisonous/very soluble/smelly

2

(b)

he

(i)

ww
w.c

(a)

ma

ctiv

(iii)

e.c

(b)

1
1

1
1

TOTAL 9

GCSE CHEMISTRY

REACTIONS & FORMULAE
ANSWERS AND MARK SCHEMES

QUESTIONSHEET 6
3.5/14 = 0.25 4/16 = 0.25
NO

1
1

(ii)

50/16 = 3.1
SO2

1
1

(iii)

39/39 = 1 1/1 = 1 12/12 = 1 48/16 = 3
KHCO3

1
1

(iv)

mass of oxygen = 16.0 − 11.2 = 4.8
4.8/16 = 0.3 11.2/56 = 0.2
Fe2O3

1
1
1

(i)

4.04/1 = 4.04 24.24/12 = 2.02 71.72/35.5 = 2.02
ratio of H:C:Cl = 2:1:1
CH2Cl

1
1
1

(ii)

relative mass of CH2Cl = 49.5
99/49.5 = 2 therefore C2H4Cl2

1
1

QUESTIONSHEET 7
(a)

(c)

om

e.c

ctiv

TOTAL 14

1

(i)

copper(II) chloride

(ii)

copper and chlorine

(iii)

bleaches
moist indicator paper

1
1

(i)

copper

1

(ii)

water

(iii)

CuO + H2 → Cu + H2O

1

(iv)

reducing agent

1

ww
w.c

(b)

copper(II) oxide

50/32 = 1.5625

ma

(b)

(i)

he

(a)

1
2

1

TOTAL 10

GCSE CHEMISTRY

REACTIONS & FORMULAE
ANSWERS AND MARK SCHEMES

QUESTIONSHEET 8
to allow you to find mass of substances in it

1

(ii)

125.9 - 117.8 = 8.1 g

1

(iii)

124.7 - 117.8 = 6.9 g

1

(iv)

8.1 - 6.9 = 1.2 g

1

(v)

1.2/8.1 × 100
= 14.8%

1
1

(d)

208

(ii)

18

e.c

(i)

moles of BaCl2 = 6.9/208 = 0.0332
moles of water = 1.2/18 = 0.0667
ratio of 1:2 therefore x = 2

QUESTIONSHEET 9
precipitation
reduction
endothermic
reversible
decomposition
oxidation
displacement
combustion

ww
w.c

(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)

ma

(c)

heat the crucible again
cool and reweigh
repeat until weight is constant

ctiv

(b)

om

(i)

he

(a)

1
1
1
1
1
1
1
1

TOTAL 14

1
1
1
1
1
1
1
1

Note: In a question of this type it is not necessary to use all the available terms.
Sometimes, a term will be required more than once.

TOTAL 8

reactions questions

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