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C6 Quick Revision Questions

C6 for AQA GCSE examination 2018 onwards

H = Higher tier only

All questions apply for combined and separate science

Question 1

• List 3 ways the time of a reaction can be measured.

.... of 50


• Loss of mass of reactant over time

• Volume of gas produced over time

• Time for a solution to become opaque or coloured

Answer 1 .... of 50


Question 2

• Name 3 pieces of apparatus used to collect gas in a chemical reaction.

.... of 50


• upturned measuring cylinder

• Upturned burette

• Gas syringe

Answer 2 .... of 50


Question 3• Add the following labels to the blanks on the

graph below• Total volume of gas produced

• Reaction has stopped

• Reaction is slower

• Reaction is fastest

.... of 50


•

Answer 3 .... of 50


Question 4• What is the time taken for the reaction to

stop?

.... of 50


• 50 seconds

Answer 4 .... of 50


Question 5

Sodium thiosulfate and hydrochloric acid are reacted to produce a precipitate of sulfur. The

reaction has finished when the X disappears on the piece of paper underneath the reaction

flask.

Give 2 reasons why this method

may lack accuracy.

.... of 50


• Different people may interpret the cross disappearing at different times

• The X on the paper could be drawn with different pens making it more/less visible

Answer 5 .... of 50


Question 6

• What does ‘in excess’ mean in a chemical reaction?

.... of 50 H


• There is more than needed of one of the reactants, therefore there will be some of this reactant left over when the reaction has finished.

Answer 6 .... of 50


Question 7

• What is the limiting reactant?

.... of 50 H


• The reactant that is used up by the end of the reaction.

Answer 7 .... of 50


Question 8

• What is the limiting reactant directly proportional to?

.... of 50 H


• The amount of product.

Answer 8 .... of 50


Question 9

• What happens to the amount of product when the amount of the limiting reactant is

doubled?

.... of 50 H


• The amount of product doubles

Answer 9 .... of 50


Question 10

Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g)

Calcium is the limiting reactant.

If 40g of Calcium react 111g of Calcium Chloride are made.

If 20g of calcium react, how much calcium chloride is made?

.... of 50 H


• 55.5g calcium chloride

Answer 10 .... of 50


Question 11

Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g)

Calcium is the limiting reactant.

If 40g of Calcium react 111g of Calcium Chloride are made.

If 65g of calcium react, how much calcium chloride is made?

.... of 50 H


• 166.5g calcium chloride



Question 12

• What is the rate of reaction?

.... of 50


• How much product is made in a reaction per second.



Question 13

• How can the rate of reaction be calculated?

.... of 50


mean rate of reaction = quantity of reactant used

time taken

or

mean rate of reaction = quantity of product formed

time taken



Question 14

• How does the rate usually change during a reaction?

.... of 50


• Reactions are usually faster at the start, then they slow down as the reactants are used up.



Question 15

• On a volume of gas/time graph, how does the gradient appear when there is a high rate of

reaction?

.... of 50


• High rate of reaction = Steep (high) gradient



Question 16

• What is meant by a horizontal line on a volume of gas/time graph

.... of 50


• The reaction has finished.



Question 17

• How is the gradient of a line calculated?

.... of 50


Question 18

• Calculate the rate of this reaction

.... of 50


• 52/25 = 2.08cm3/s



Question 19

• 50cm3 of carbon dioxide gas is made in 20seconds. Calculate the rate of reaction.

.... of 50


• 2.5cm3/s



Question 20

• List the factors affecting the rate of a chemical reaction (there’s 5!)

.... of 50


• Temperature

• Concentration of reactants

• Pressure of reacting gases

• Surface area of solid reactants

• catalyst



Question 21

• How does temperature affect the rate of reaction?

.... of 50


• Increase temperature causes an increase in rate of reaction

Answer21 .... of 50


Question 22

• How does the surface area of solid particle reactants affect the rate of reaction?

.... of 50


• Small particles have greater surface area therefore a higher rate of reaction



Question 23• Which line shows the higher concentration of

acid?

.... of 50


•



Question 24• Which line shows the higher mass of

Magnesium used in a reaction with hydrochloric acid?

.... of 50


•



Question 25

• Which line shows the highest temperature?

.... of 50


•



Question 26

• What needs to happen in order for a reaction to take place?

.... of 50


• Reactant particles need to collide with sufficient energy for a reaction to take place



Question 27

• What is the name given to the minimum energy needed for a reaction to take place?

.... of 50


• Activation energy



Question 28

• Which has the highest rate of reaction, a high or a low concentration of reactant? Use the

collision theory to explain your answer.

.... of 50


• Higher concentration has a higher rate of reaction

• Higher concentration has more particles in the same volume

• Therefore the particles are more crowded

• Therefore more successful collisions per second (or a higher collision frequency)



Question 29

• Which has the highest rate of reaction, a high or a low temperature? Use the collision theory

to explain your answer.

.... of 50


• Higher temperature reactions have a higher rate of reaction

• Higher temperature means the reacting particles have more kinetic energy

• Therefore more particles reacting with the minimum activation energy




Question 30

• Which has the highest rate of reaction, a high or a low pressure of gaseous reactant? Use the collision theory to explain your answer.

.... of 50


• Higher pressure has a higher rate of reaction

• Higher pressure has more particles in the same volume

• Therefore the particles are more crowded




Question 31

• What is a catalyst?

.... of 50


• A substance that speeds up the rate of a chemical reaction but is not used up in the reaction.



Question 32

• Catalysts are specific, what does this mean?

.... of 50


• Each catalyst only works for one single reaction. A certain catalyst will not speed up all types of reactions.



Question 33

• How does a catalyst work?

.... of 50


• It lowers the activation energy so more of the collisions that take place are successful.



Question 35• On this energy profile diagram, which

pathway shows a catalyst?

.... of 50


•



Question 36

• What is the symbol used for a reversible reaction?

.... of 50


•



Question 37

• What is a reversible reaction?

.... of 50


• reactants form products and products can also form reactants



Question 38

• How can the direction of reversible reactions be changed?

.... of 50 H


By changing conditions such as

• Temperature

• Concentrations of reactants and products

• pressure



Question 39

• What happens when the forward and the backwards reactions are happening at the

same rate?

.... of 50


• The reaction is at equilibrium



Question 40

• How is a closed system achieved?

.... of 50


• The apparatus prevents products and reactants from escaping



Question 41

• What is the same when a reaction is in equilibrium?

.... of 50


• The rates of the forwards and backwards reactions. The concentrations of the reactants and products do not have to be equal.



Question 42

• What is Le Chatelier’s principle?

.... of 50 H


• If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.



Question 43

2SO2(g) + O2(g) 2SO3(g)

Using Le Chatelier’s principle, what will happen if the concentration of O2 is decreased?

.... of 50 H


• The amount of product (SO3) will decrease in order to produce more O2 and restore the equilibrium.



Question 44

2SO2(g) + O2(g) 2SO3(g)

Using Le Chatelier’s principle, what can you remove to produce more product?

.... of 50 H


• SO3



Question 45

• Why is the Contact process important in industry?

.... of 50 H


• Sulfur trioxide is used to make sulfuric acid which makes fertilisers, paints and plastics.



Question 46

N2(g) + 3H2(g) 2NH3(g)

The forward reaction is exothermic

How could you change the temperature to increase the yield of the reaction?

.... of 50 H


• Decreasing the temperature will increase the forward reaction producing more product.



Question 47

N2(g) + 3H2(g) 2NH3(g)

The forward reaction is exothermic

Why is a temperature of 450oC used?

.... of 50 H




• Compromise – low temperature is needed to favour exothermic reaction, but a higher

temperature is needed to speed up the rate of reaction

Question 48

N2(g) + 3H2(g) 2NH3(g)

How many moles on the product side?

How many moles on the reactant side?

.... of 50 H


Reactants – 4

Products - 2



Question 49

N2(g) + 3H2(g) 2NH3(g)

How should the pressure be changed to increase the yield?

.... of 50 H


• Increase the pressure to favour the product side (which has less moles) and therefore shift the equilibrium to the right.



Question 50

2SO2(g) + O2(g) 2SO3(g)

What affect you increasing the pressure have on the Contact process?

.... of 50 H


• Therefore are fewer number of moles on the products side, therefore increasing the pressure would favour the forward reaction therefore increasing the yield of product



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