Practice paper

Question 1

Why do alkaline batteries eventually stop working?

Answer 1

A reactant is used up

Question 2

Why can alkaline batteries not be charged?

Answer 2

The reaction is not reversible

Question 3

Evaluate the use of hydrogen fuel cells with rechargeable lithium ion batteries

Answer 3

Overall my judgement is that hydrogen fuel cells are better for a number of reasons. For example the table clearly shows a significantly shorter refueling time and a far greater range. From my own knowledge, I know that hydrogen fuel cells do not produce any form of pollutants, only water, while lithium iron batteries can be known to release toxic chemicals when they are disposed of. So overall, I would say hydrogen fuel cells would be better to power an electric car.

Question 4

The student concluded that that the reactions between the metals and copper sulfate solution are endothermic
Give one reason why this conclusion is wrong

Answer 4

Because there was an increase in temperature

Question 5

Describe a method to find the position of an unknown metal in this reactivity series

Answer 5

• Add the unknown metal to copper sulfate
• Measure the temperature change
• Place metals in order of the change in temperature

Question 6

Explain why electrolysis would not take place in the apparatus shown in figure 6

Answer 6

The solid zinc chloride does not conduct electricity because ions cannot move around in a solid

Question 7

explain why graphite conducts electricity

Answer 7

because each atom forms 3 bonds and one electron per atom is delocalised, meaning it can carry charge around the graphite

Question 8

Student 1 made an error in selecting apparatus for this investigation (figure 7). How should it be changed

Answer 8

Use burette so that volume can be measured

Question 9

Describe the trends shown in the results of figure 8

Answer 9

• The hydrogen is collected at a steady rate
• Chlorine is collected at an increasing rate up to 8 minutes
• hydrogen is collected at a rate of 0.45 (cm3/min)

Question 10

Select one reason for the difference in volume of each gas collected in figure 8

Answer 10

chlorine reacts with water

Question 11

calculate the amount in moles of chlorine collected after 20 minutes. Use figure 8. The volume of any gas at room temperature and pressure is 24.0 dm(3) Give your answer in standard form

Answer 11

volume = 6.6/1,000 = 0.0066
moles = 0.0066/24 = 2.75 X 10(-4)

Question 12

Name the products formed when chlorine solution reacts with potassium iodine solution

Answer 12

potassium chloride + iodine

Question 13

Explain why chlorine is more reactive than iodine

Answer 13

The outer electrons of chlorine are closer to the nucleus so chlorine has less shielding. this means it can gain electron easier

Question 14

Chlorine reacts with hydrogen to form hydrogen chloride. Explain why hydrogen is a gas at room temperature.

Answer 14

It is made of small molecules that mean it has weak intermolecular forces between bonds, so not much energy is required to overcome them

Question 15

Calculate the bond energy X for the C-BR bond using figure 9 and table 3

Answer 15

412 + 193 = 605
- 51 = 605 - (366 + X)
X = 290 kj/mol