C6 Quick Revision Questions

Transcription

1 C6 Quick Revision Questions H = Higher tier only All questions apply for combined and separate science

2 Question 1... of 50 List 3 ways the time of a reaction can be measured.

3 Answer 1... of 50 Loss of mass of reactant over time Volume of gas produced over time Time for a solution to become opaque or coloured

4 Question 2... of 50 Name 3 pieces of apparatus used to collect gas in a chemical reaction.

5 Answer 2... of 50 upturned measuring cylinder Upturned burette Gas syringe

6 Question 3... of 50 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

7 Answer 3... of 50

8 Question 4... of 50 What is the time taken for the reaction to stop?

9 Answer 4... of seconds

10 Question 5... of 50 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.

11 Answer 5... 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

12 Question 6... of 50 H What does in excess mean in a chemical reaction?

13 Answer 6... of 50 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.

14 Question 7... of 50 H What is the limiting reactant?

15 Answer 7... of 50 The reactant that is used up by the end of the reaction.

16 Question 8... of 50 H What is the limiting reactant directly proportional to?

17 Answer 8... of 50 The amount of product.

18 Question 9... of 50 H What happens to the amount of product when the amount of the limiting reactant is doubled?

19 Answer 9... of 50 The amount of product doubles

20 Question of 50 H Ca (s) + 2HCl (aq) CaCl 2(aq) + H 2(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?

21 Answer of g calcium chloride

22 Question of 50 H Ca (s) + 2HCl (aq) CaCl 2(aq) + H 2(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?

23 Answer of g calcium chloride

24 Question of 50 What is the rate of reaction?

25 Answer of 50 How much product is made in a reaction per second.

26 Question of 50 How can the rate of reaction be calculated?

27 Answer of 50 mean rate of reaction = quantity of reactant used time taken or mean rate of reaction = quantity of product formed time taken

28 Question of 50 How does the rate usually change during a reaction?

29 Answer of 50 Reactions are usually faster at the start, then they slow down as the reactants are used up.

30 Question of 50 On a volume of gas/time graph, how does the gradient appear when there is a high rate of reaction?

31 Answer of 50 High rate of reaction = Steep (high) gradient

32 Question of 50 What is meant by a horizontal line on a volume of gas/time graph

33 Answer of 50 The reaction has finished.

34 Question of 50 How is the gradient of a line calculated?

35 Answer of 50

36 Question of 50 Calculate the rate of this reaction

37 Answer of 50 52/25 = 2.08cm 3 /s

38 Question of 50 50cm 3 of carbon dioxide gas is made in 20seconds. Calculate the rate of reaction.

39 Answer of cm 3 /s

40 Question of 50 List the factors affecting the rate of a chemical reaction (there s 5!)

41 Answer of 50 Temperature Concentration of reactants Pressure of reacting gases Surface area of solid reactants catalyst

42 Question of 50 How does temperature affect the rate of reaction?

43 Answer21... of 50 Increase temperature causes an increase in rate of reaction

44 Question of 50 How does the surface area of solid particle reactants affect the rate of reaction?

45 Answer of 50 Small particles have greater surface area therefore a higher rate of reaction

46 Question of 50 Which line shows the higher concentration of acid?

47 Answer of 50

48 Question of 50 Which line shows the higher mass of Magnesium used in a reaction with hydrochloric acid?

49 Answer of 50

50 Question of 50 Which line shows the highest temperature?

51 Answer of 50

52 Question of 50 What needs to happen in order for a reaction to take place?

53 Answer of 50 Reactant particles need to collide with sufficient energy for a reaction to take place

54 Question of 50 What is the name given to the minimum energy needed for a reaction to take place?

55 Answer of 50 Activation energy

56 Question of 50 Which has the highest rate of reaction, a high or a low concentration of reactant? Use the collision theory to explain your answer.

57 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)

58 Question of 50 Which has the highest rate of reaction, a high or a low temperature? Use the collision theory to explain your answer.

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

60 Question of 50 Which has the highest rate of reaction, a high or a low pressure of gaseous reactant? Use the collision theory to explain your answer.

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

62 Question of 50 What is a catalyst?

63 Answer of 50 A substance that speeds up the rate of a chemical reaction but is not used up in the reaction.

64 Question of 50 Catalysts are specific, what does this mean?

65 Answer of 50 Each catalyst only works for one single reaction. A certain catalyst will not speed up all types of reactions.

66 Question of 50 How does a catalyst work?

67 Answer of 50 It lowers the activation energy so more of the collisions that take place are successful.

68 Question of 50 On this energy profile diagram, which pathway shows a catalyst?

69 Answer of 50

70 Question of 50 What is the symbol used for a reversible reaction?

71 Answer of 50

72 Question of 50 What is a reversible reaction?

73 Answer of 50 reactants form products and products can also form reactants

74 Question of 50 H How can the direction of reversible reactions be changed?

75 Answer of 50 By changing conditions such as Temperature Concentrations of reactants and products pressure

76 Question of 50 What happens when the forward and the backwards reactions are happening at the same rate?

77 Answer of 50 The reaction is at equilibrium

78 Question of 50 How is a closed system achieved?

79 Answer of 50 The apparatus prevents products and reactants from escaping

80 Question of 50 What is the same when a reaction is in equilibrium?

81 Answer of 50 The rates of the forwards and backwards reactions. The concentrations of the reactants and products do not have to be equal.

82 Question of 50 H What is Le Chatelier s principle?

83 Answer of 50 If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.

84 Question of 50 H 2SO 2(g) + O 2(g) 2SO 3(g) Using Le Chatelier s principle, what will happen if the concentration of O 2 is decreased?

85 Answer of 50 The amount of product (SO 3 ) will decrease in order to produce more O 2 and restore the equilibrium.

86 Question of 50 H 2SO 2(g) + O 2(g) 2SO 3(g) Using Le Chatelier s principle, what can you remove to produce more product?

87 SO 3 Answer of 50

88 Question of 50 H Why is the Contact process important in industry?

89 Answer of 50 Sulfur trioxide is used to make sulfuric acid which makes fertilisers, paints and plastics.

90 Question of 50 H N 2(g) + 3H 2(g) 2NH 3(g) The forward reaction is exothermic How could you change the temperature to increase the yield of the reaction?

91 Answer of 50 Decreasing the temperature will increase the forward reaction producing more product.

92 Question of 50 H N 2(g) + 3H 2(g) 2NH 3(g) The forward reaction is exothermic Why is a temperature of 450 o C used?

93 Answer of 50 Compromise low temperature is needed to favour exothermic reaction, but a higher temperature is needed to speed up the rate of reaction

94 Question of 50 H N 2(g) + 3H 2(g) 2NH 3(g) How many moles on the product side? How many moles on the reactant side?

95 Answer of 50 Reactants 4 Products - 2

96 Question of 50 H N 2(g) + 3H 2(g) 2NH 3(g) How should the pressure be changed to increase the yield?

97 Answer of 50 Increase the pressure to favour the product side (which has less moles) and therefore shift the equilibrium to the right.

98 Question of 50 H 2SO 2(g) + O 2(g) 2SO 3(g) What affect you increasing the pressure have on the Contact process?

99 Answer of 50 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