Chemistry Paper 2 Mistakes

Question 1

Which of these describes the element iodine at room temperature?

Answer 1

Grey Solid

Question 2

Answer 2

white solid/powder/ash

Question 3

Aluminium is a metal with many uses.
Aluminium is malleable, a good conductor of heat and electricity, and has a low density compared to most other metals.
Explain two uses of aluminium that are related to its properties.
(4)

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

Answer 8

X = PIPETTE
Y = BURETTE

Question 9

(Volume of Nitric acid = 31.4).
Calculate the volume, in cm3 of carbon dioxide gas at rtp that would be produced from the 25.0cm3 of the sodium carbonate solution
[at rtp, molar volume = 24 000cm3]

Answer 9

Question 10

Describe a test to show that sodium carbonate solution contains carbonate ions.
(3)

Answer 10

Question 11

If the solution is dilute, a significant amount of oxygen collects at P.
Complete the ionic half-equation for this reaction.
(1)
…………….H2O → …………….H+
+ …………….O2 + …………….e

Answer 11

Question 12

Explain how hydrogen gas forms at the negative electrode

Answer 12

Question 13

Complete the diagram to show the energy levels of the reactants and
products, and the enthalpy change, ΔH.

Answer 13

Question 14

Answer 14

Question 15

A student is given an aqueous solution of chlorine and an aqueous solution of sodium iodide.
The student mixes the two solutions.
Explain the colour change that occurs

Answer 15

M1 (mixture) turns (from colourless) to brown
M2 iodine / I2 is displaced

Question 16

State what is meant by the term alloy.

Answer 16

(an alloy is) a mixture of metals

Question 17

(see diagram) - Give a reason why refinery gases rise to the top of the column

Answer 17

refinery gases have the low(est) boiling point
OR
refinery gases do not condense in the column

Question 18

Describe the forces of attraction in metallic bonding.

Answer 18

M1 (electrostatic attraction between) positive ions
M2 (and) delocalised electrons

Question 19

Explain why lithium is less reactive than potassium.
Refer to atomic structure in your answer.

Answer 19

M1 lithium has fewer shells than potassium
M2 outer shell / outer electron in lithium is more strongly attracted to the nucleus
M3 (so in lithium the outer shell) electron is less easily lost

Question 20

Answer 20

M1 the forward and reverse reactions occur at the same rate
M2 so the concentrations of reactants and products remain constant

Question 21

Give a reason why adding a catalyst does not affect the yield of methanol.

Answer 21

a catalyst increases the rate of (both) the forwards and the reverse reaction EQUALLY

Question 22

The temperature of the reaction mixture is decreased at constant pressure.
Explain the effect of this change on the yield of methanol.

Answer 22

M1 yield increases
M2 the (forward) reaction is exothermic

Question 23

The pressure of the reaction mixture is increased at constant temperature.
Explain the effect of this change on the yield of methanol

Answer 23

M1 yield increases
M2 there are more moles of (gaseous) reactants
than products

Question 24

Explain why this reaction is exothermic.

Answer 24

M1 more energy is given out when the bonds are made
M2 than is taken in when the bonds are broken

Question 25

Which colour change occurs when copper(II) carbonate is heated? A blue to black B blue to orange C green to black D green to orange

Answer 25

C (green to black) A is incorrect as copper(II) carbonate is not blue B is incorrect as copper(II) carbonate is not blue and copper(II) oxide is not orange D is incorrect as copper(II) oxide is not orange

Question 26

Answer 26

Question 27

Explain one advantage and one disadvantage of using fermentation rather than hydration to produce ethanol. You should use information from the table to help your answer.

Answer 27

advantage: M1 uses low(er) pressure / atmospheric pressure M2 so less energy needed / less costly equipment / safer OR M1 uses low(er) temperature M2 so less energy / heat needed OR M1 glucose /sugar cane is a natural resource /is renewable M2 whereas ethene obtained from crude oil /ethene is non-renewable / ethene is a finite resource OR M1 yeast is a natural resource M2 whereas phosphoric acid is a manufactured catalyst disadvantage: M3 fermentation is slow(er) M4 fermentation is less efficient /so hydration is more efficient OR M3 ethanol is impure M4 so ethanol needs to be purified OR M3 growing sugar cane takes up land M4 that can be used to grow food crops

Question 28

Explain why fermentation needs to occur in the absence of air.

Answer 28

M1 oxygen would oxidise / react with ethanol / alcohol M2 which would produce ethanoic acid / CH3COOH OR M1 fermentation needs to be anaerobic M2 so ethanol / alcohol will be formed / otherwise only carbon dioxide and water would form

Question 29

Give the colour of methyl orange in potassium hydroxide solution and in dilute sulfuric acid.

Answer 29

M1 (colour in potassium hydroxide) yellow M2 (colour in sulfuric acid) red

Question 30

Answer 30

Question 31

Answer 31

M1 add sodium hydroxide (to the copper(II) sulfate solution) M2 blue precipitate (forms) OR M1 flame test M2 blue-green (flame)

Question 32

Describe how copper metal forms at the negative electrode.

Answer 32

Question 33

Answer 33

Question 34

Ethanoic acid reacts with methanol to form an ester. Give the name of this ester.

Answer 34

methyl ethanoate

Question 35

Answer 35

C⎯O and O⎯H

Question 36

Explain why the enthalpy change in this reaction is approximately 0kJ/mol.

Answer 36

M1 the same (two) bonds / C⎯O and O⎯H are broken and formed M2 energy needed to break bonds equals energy released when bonds form (so overall enthalpy change is 0)

Question 37

The reaction conditions for this reaction (see picture) are a temperature of 700°C and a pressure of 5 atmospheres. (i) The temperature of the reaction mixture is reduced to 600°C, but the pressure is kept at 5 atmospheres. Explain the effect on the yield of hydrogen at equilibrium.

Answer 37

M1 yield decreases M2 as (forward) reaction is endothermic (so equilibrium shifts to the LHS / reactants side)

Question 38

The pressure of the reaction mixture is reduced to 4 atmospheres, but the temperature is kept at 700°C. Explain the effect on the yield of hydrogen at equilibrium.

Answer 38

M1 yield increases M2 as there are fewer moles / molecules (of gas) on the left-hand side

Question 39

Calculate the volume, in dm3 , of methane gas at rtp needed to produce 6.6 tonnes of hydrogen gas. [at rtp, molar volume = 24dm3 1 tonne = 106 g] Give your answer in standard form

Answer 39

M1 n(H2) = 6.6 × 106 ÷ 2 OR 3.3 × 106(mol) M2 n(CH4) = 3.3 × 106 ÷ 3 OR 1.1 × 106(mol) M3 vol(CH4) = 1.1 × 106 × 24 OR 26 400 000 (dm3) M4 2.6 × 107