Question
This question is about acids, bases and salts.
(a) Sodium hydroxide is a base.
(i) Name the products formed when sodium hydroxide reacts with dilute nitric acid.[2]
(ii) Describe the effect of sodium hydroxide on a named indicator.[2]
(iii) Complete the word equation for the reaction of sodium hydroxide with ammonium chloride.
(b) Describe how to prepare pure, dry crystals of the salt zinc sulfate from an aqueous solution of zinc sulfate.[2]
(c) The rate of reaction of zinc powder with dilute sulfuric acid is found by measuring the increase in volume of hydrogen gas produced as time increases.
Describe the effect, if any, of each of the following on the rate of this reaction.
-
- The reaction is carried out with large pieces of zinc instead of zinc powder.
All other conditions stay the same.
-
- The reaction is carried out using a catalyst.
All other conditions stay the same.
-
- The reaction is carried out with dilute sulfuric acid of a lower concentration.
All other conditions stay the same. [3] [Total: 11]
Answer/Explanation
Ans:
(a)(i) sodium nitrate (1)
(and) water (1)
(a)(ii) named suitable indicator e.g. methyl orange / litmus (1)
correct colour in alkali e.g. blue (for litmus) / yellow (for methyl orange) (1)
(a)(iii) ammonia (1)
sodium chloride (1)
(b) 1 mark each for any two of:
-
- evaporate to point of crystallisation / heat to point of crystallisation / evaporate some of the water and leave (1)
- filter crystals / pick out crystals (1)
- dry with filter paper / dry in drying oven
(c) large pieces: (rate) decreases / (reaction gets) slower (1)
catalyst: (rate) increases / (reaction gets) faster (1)
lower concentration: (rate) decreases / (reaction gets) slower (1)
Question
This question is about metals and compounds of metals.
(a) Identify two correct statements about transition elements. Tick two boxes.
(b) The table compares the ease of reduction of some metal oxides with carbon.
Put the four metals in order of their reactivity.
Put the least reactive metal first.
(c) Crystals of copper(II) sulfate, $\mathrm{CuSO}_4 \cdot 5 \mathrm{H}_2 \mathrm{O}$, can be prepared by heating excess copper(II) oxide powder with dilute sulfuric acid.
(i) Describe how to prepare a sample of pure dry copper(II) sulfate crystals after the reaction is complete.
In your answer describe how to:
- remove the excess copper(II) oxide from the reaction mixture
- crystallise the copper(II) sulfate
- dry the crystals. [4]
(ii) Identify the word that best describes copper(II) sulfate.
Draw a circle around the correct answer.
acid $\bigcirc$
halogen $\bigcirc$
polymer $\bigcirc$
salt $\bigcirc$ [1]
(d) A few drops of water are added to a sample of solid anhydrous copper(II) sulfate, $\mathrm{CuSO}_4$.
(i) The reaction is reversible.
$$
\mathrm{CuSO}_4+5 \mathrm{H}_2 \mathrm{O} \quad\square\quad \mathrm{CuSO}_4 \cdot 5 \mathrm{H}_2 \mathrm{O}
$$
Draw in the box, the sign for a reversible reaction. [1]
(ii) State the colour change observed when water is added to anhydrous copper(II) sulfate.
from —————– to ——————————– [2] [Total: 12]
▶️Answer/Explanation
Ans:
(a)$2^{\text {nd }}$ box down ticked (have high densities) (1)
$4^{\text {th }}$ box down ticked (high melting points) (1)
(b) copper<cobalt<manganese<magnesium (2)
If 2 marks not scored one mark for one consecutive pair reversed / all reversed
(c)(i) one mark each for any four of:
• filter (off copper oxide)
• warm (or heat or evaporate) filtrate to point of crystallisation / warm filtrate to form saturated solution / heat filtrate until
crystals start to form
• filter off crystals / pick out crystals
• wash crystals with cold water / wash crystals with (organic) solvent
• dry crystals with filter paper
(c)(ii) salt
(d)(i) ⇌
8(d)(ii) white (1)
(to) blue (1)
Question
This question is about the reactions of magnesium with nitric acid.
(a) The equation for the reaction of magnesium with concentrated nitric acid is shown.
\(Mg + 4HNO_3 → Mg(NO_3)_2 + 2NO_2 + 2H_2O\)
(i) The reaction is exothermic.
What is the meaning of the term exothermic?
(ii) Which word best describes the compound Mg(NO3)2?
Draw a circle around the correct answer.
acid base oxide salt
(iii) Oxides of nitrogen are formed when fossil fuels are burned.
What type of chemical reaction occurs when fossil fuels are burned?
Draw a circle around the correct answer.
combustion cracking fermentation neutralisation
(iv) Oxides of nitrogen dissolve in rain water to form acid rain.
State one adverse effect of acid rain on buildings.
(b) When very dilute nitric acid reacts with magnesium powder, hydrogen is produced.
(i) Describe a practical method for investigating the rate of this reaction.
(ii) What effect would each of the following have on the rate of this reaction?
● Larger pieces of magnesium are used instead of magnesium powder.
All other conditions stay the same.
……………………………………………………………………………………………………………………………
● The temperature of the reaction mixture is increased.
All other conditions stay the same.
Answer/Explanation
Answer:
(a) (i) transfers thermal energy to surrounding / transfers heat to surroundings / gives out heat
(ii) salt
(iii) combustion
(iv) (chemical) erosion (of mortar / building materials) / corrodes (iron)
(b) (i) measure volume of gas / measure volume of hydrogen / idea of measuring mass of the reaction mixture (1)
reference to (measurement at certain) time(s) (1)
suitable collection apparatus related to method suggested, e.g. gas syringe / upturned measuring cylinder (over
water) / balance (1)
(ii) large pieces: (rate) decreases / gets slower / slows down (1)
increasing temperature: (rate) increases / gets faster (1)