Chemistry paper exam questions 2

Question 1

Reversible reactions can reach equilibrium in a closed system. What is a closed system

Answer 1

nothing can enter

Question 2

explain why when a reversible reaction reaches equilibrium, the reaction appears to have stopped

Answer 2

because forward and backward reactions have the same rate and there is no overall change in the quantity of products and reactants

Question 3

Name a natural resource from which hydrogen is produced.

Answer 3

natural gas

Question 4

The Haber process uses a catalyst to speed up the reaction.

Explain how a catalyst speeds up a reaction

Answer 4

They speed up the reaction by reducing the activation energy (lower the activation energy) and providing a different pathway for the reaction

Question 5

What happens to the amount of ammonia produced at equilibrium if the pressure is
increased?
Give a reason for your answer.

Answer 5

when the pressure is increased the equilibrium moves to the side of the equation with fewer moles of gas therefore the amount of ammonia increases

Question 6

How does the diagram show that the reaction is endothermic?

Answer 6

the energy of the products is higher than the energy of the reactants

Question 7

Suggest what effect, if any, increasing the temperature will have on the amount of
hydrogen iodide at equilibrium.
Give a reason for your answer.

Answer 7

the amount of hydrogen iodide decreases and the equilibrium moves in the direction of the endothermic reaction.

Question 8

Suggest two reasons why all of the points do not lie on the line of best fit

Answer 8

results not recorded correctly

plotting error

Question 9

In a conclusion to the investigation, the student stated that:
‘The rate of this reaction is directly proportional to the concentration of the sodium
thiosulfate solution.’
How does the graph support this conclusion?

Answer 9

the graph goes in a straight line

Question 10

Explain, in terms of particles, why the rate of reaction increases when the
the concentration of sodium thiosulfate is increased.

Answer 10

The particles are closer and collide more successfully

Question 11

Explain, in terms of particles, why temperature has this effect on the rate of reaction.
To gain full marks in this question you should write your ideas in good English.
Put them into a sensible order and use the correct scientific words.

Answer 11

increasing the temperature increases the rate of a reaction because the particles can move faster as they have more energy and between the particles increase. Therefore more particles have activation energy.

Question 12

State one variable that must be kept constant to make this experiment a fair test.

Answer 12

the rate of stirring

Question 13

Phosphoric acid is made by reacting phosphate rock with sulfuric acid.
Only three of the methods shown below will increase the rate of this reaction.
Put a tick next to each of the three methods that will increase the rate of this reaction.

Answer 13

• use a more concentrated solution of sulfuric acid
• Grind the phosphate rock into a powder before adding the acid
• increase the temperature of the sulfuric acid

Question 14

Information about car engines. Complete the sentence with the correct word

Answer 14

The exothermic reaction makes the temperature of the engine increase.

This is because during the exothermic reactions energy is given out to the surroundings.

Question 15

The equation for the reaction that takes place in part A is:
2NO → N2 + O2
Which one of the substances shown in the equation is a compound?
Give the formula of this compound.

Answer 15

2no

Question 16

why is it important to stop carbon monoxide from being released into the air

Answer 16

harmful

Question 17

The table lists some statements about catalysts. Only two statements are correct

Answer 17

a catalyst can speed up a chemical reaction.

Different reactions need different catalysts.

Question 18

Modern catalytic converters contain nanosized particles of catalyst.
Less catalyst is needed when nanosized catalyst particles are used.
Complete the sentence

Answer 18

The size of nanosized particles is smaller than normal sized

particles.

Question 19

The catalysts contain platinum.

Suggest why a manufacturer of catalytic converters would want to use less catalyst.

Answer 19

save resources

Question 20

The teacher said that the student should repeat the investigation to get more results.
Suggest why.

Answer 20

to make it accurate

Question 21

The rate of reaction between sulfuric acid and phosphate rock can be increased if the
mixture is heated to a higher temperature.
Explain, in terms of particles, why an increase in temperature increases the rate of
reaction.

Answer 21

particles move faster and have more energy

Question 22

State one other way in which the rate of reaction between sulfuric acid and phosphate rock
can be increased.

Answer 22

adding a catalyst

Question 23

The equation for the reaction is:
Na2S2O3(aq) + 2 HCl(aq) → 2 NaCl(aq) + H2O(l) + SO2(g) + S(s)
(a) Explain why the solution goes cloudy.

Answer 23

because sulfur forms which is a solid

Question 24

Describe and explain, in terms of particles and collisions, the effect that increasing
the concentration of sodium thiosulfate has on the rate of the reaction

Answer 24

The reaction rate increases as more reacting particles there are because the more particles increase the number of collisions also increases.

Question 25

Complete the word equation for the reaction of sulfur dioxide with oxygen.

Answer 25

sulfur dioxide + oxygen – sulfur trioxide

Question 26

Draw a ring around the correct answer to complete the sentence.

Answer 26

Sulfur dioxide (SO2) is
a compound.(the correct answer)
an element.
a mixture.

Question 27

The reactants are gases.
When the pressure of the gases is increased, the reaction gets faster.
Complete the sentence.

Answer 27

When the pressure of the gases is increased,

the frequency of the collisions increases.

Question 28

The particles need the energy to react.

Complete the sentence.

Answer 28

The minimum amount of energy that particles need to react is called
the activation energy.

Question 29

Give one way of increasing the rate of the reaction other than changing the pressure.

Answer 29

by adding a catalyst

Question 30

What volume of gas has been collected?

Answer 30

Volume = 36 cm3

Question 31

What are two possible reasons for the anomalous result?

Answer 31

The bung was not pushed in firmly enough.
The measuring cylinder was not completely over
the delivery tube

Question 32

Describe the pattern the graph shows up to 0.4 g of lithium carbonate added.

Answer 32

As the mass of lithium carbonate increases the volumes of gas increase ( linear proportional )

Question 33

The equation shows the decomposition of lithium carbonate.
Li2CO3 (s) → Li2O (s) + CO2 (g)
Figure 4 shows the apparatus a student used to decompose lithium carbonate.
Why does the limewater bubble?

Answer 33

carbon dioxide is produced

Question 34

The student repeated the experiment with potassium carbonate.
The limewater did not bubble.
Suggest why there were no bubbles in the limewater.

Answer 34

potassium carbonate does not decompose to produce carbon dioxide

Question 35

State one conclusion the student could make about the effect of temperature on the
rate of the reaction.

Answer 35

the higher the temperature, the faster the reaction

Question 36

Give one reason why the student could make this conclusion

Answer 36

40 degrees Celsius line becomes a horizontal line sooner than 20 degrees Celsius.

Question 37

Which two variables should the student keep constant?

Answer 37

• concentration of acid

- mass of marble chips

Question 38

Explain, in terms of particles and collisions, the effect that increasing the surface area
of the marble chips has on the rate of reaction.

Answer 38

increases rate because the particles are more likely to collide

Question 39

Calcium carbonate is a catalyst for the industrial production of biodiesel.
Give one reason why using a catalyst reduces costs.

Answer 39

increases the rate of the reaction

Question 40

The equation for the reaction is:
Na2S2O3(aq) + 2 HCl(aq) 2 NaCl(aq) + S(s) + SO2(g) + H2O(l)
Name the product that made the mixture go cloudy.

Answer 40

sulfur

Question 41

Describe the trends shown in the student’s results.

Answer 41

the rate of reaction increases slowly (from 20 °C to 50 °C)

then increases more rapidly

Question 42

Suggest two variables the student would need to control to make sure that her
results were valid.

Answer 42

they need to control the temperature of the reactants and the amount of sodium thiosulfate

Question 43

From this investigation the student correctly concluded:
‘As the concentration of sodium thiosulfate solution doubles, the rate of reaction
doubles.’
Explain the student’s conclusion in terms of particles

Answer 43

because the concentration increases the particles are together and the reaction rate increases. Therefore the frequency of collisions increases so the frequency of collisions doubles.

Question 44

A student investigated the rate of reaction between marble chips and hydrochloric acid.
Figure 1 shows the apparatus the student used.
What is A?

Answer 44

cotton wool

Question 45

The equation for the reaction is:
2HCl(aq) + CaCO3(s) → CaCl2(aq) + H2O(l) + CO2(g)
Explain why there is a loss in mass in this investigation.

Answer 45

because there is a gas produced which escapes from the flask

Question 46

The student measured the change in mass of the reactants.
Describe another method, other than measuring the change in mass of the reactions, that
the student could have used to find the rate of the reaction between marble chips and
hydrochloric acid.

Answer 46

the other methods could be counting the bubbles or collecting the gas in a gas syringe

Question 47

Another student planned to investigate the effect of temperature on the rate of reaction.
The student predicted that the rate of reaction would increase as the temperature was
increased.
Give two reasons why the student’s prediction is correct.

Answer 47

The particles have more energy.

The particles move faster.

Question 48

Marble chips are mainly calcium carbonate (CaCO3).
A student investigated the rate of reaction between marble chips and hydrochloric acid (HCl).
Figure 1 shows the apparatus the student used.
Figure 1
(a) Complete and balance the equation for the reaction between marble chips and hydrochloric
acid.

Answer 48

…..caco3…………. + ……2hcl………… → CaCl2 + …..h20…………. + ……….c20……..

Question 49

Explain, in terms of particles, how and why the rate of reaction changes during the reaction
of calcium carbonate with hydrochloric acid.

Answer 49

the acid particles are used up so the concentration decreases, this means that there is less frequent collisions per second and the rate of the reaction slows down

Question 50

Explain why the solution goes cloudy.

Answer 50

because of sulfur which is a solid

Question 51

Give two variables the student must control to make the investigation a fair test.

Answer 51

• concentration of sodium thiosulfate

- concentration of hydrochloric acid

Question 52

State the effect that increasing the temperature of the sodium thiosulfate solution has on
the rate of the reaction.
Explain this effect in terms of particles and collisions.

Answer 52

Increasing the temperature increases the rate of the reaction because particles have more energy, therefore, increasing the frequency of collisions between the particles. Additionally, more particles have energy greater than the activation energy