Separate Chemistry 1Edexcel GCSE Chemistry: Topic test

20 questions, 54 marks

Edexcel GCSE Chemistry

Separate Chemistry 1 topic test

Total 54 marks

Name

Class

Date

1
A materials technician examines three samples for a school open day: a lump of pure copper, a block of bronze (an alloy of copper and tin), and a small amount of black manganese(IV) oxide powder. She adds the manganese(IV) oxide to a test tube of hydrogen peroxide solution, and observes rapid effervescence, with a glowing splint relighting when held at the mouth of the tube; the powder itself remains unchanged in mass once the effervescence has finished.
(a)
Which property is being shown by the manganese(IV) oxide in this experiment?
[1 mark]
ATransition metals and their compounds often act as catalysts, speeding up a reaction such as the decomposition of hydrogen peroxide, without being used up themselves
BTransition metals and their compounds always have low melting points and low densities compared with other metals
CTransition metals and their compounds never form coloured substances, since manganese(IV) oxide is black rather than coloured
DTransition metals are non-metals that conduct electricity because of delocalised protons moving through the structure
(b)
Bronze is harder than pure copper. Which explanation best accounts for this, using the particle model of alloys?
[1 mark]
ABronze forms stronger covalent bonds between copper and tin atoms than the metallic bonds present in pure copper
BBronze contains atoms of different sizes (copper and tin), which distorts the regular layers of atoms and makes it harder for the layers to slide over one another
CThe tin atoms in bronze react chemically with the copper atoms to form a giant ionic lattice
DBronze contains no delocalised electrons at all, so its layers of atoms cannot move past each other
(c)
Unprotected iron nails placed next to the samples would soon start to corrode. Explain what two substances must both be present for iron to rust, and describe one way of protecting the iron nails from rusting by excluding one of these substances.
[2 marks]
Total for question 1: 4 marks
2
A student heats 2.43 g of magnesium ribbon in an open crucible until it has fully reacted with the oxygen in the air, forming a white powder of magnesium oxide. Using the balanced equation 2Mg + O2 -> 2MgO and relative atomic masses Mg = 24 and O = 16, the theoretical (maximum) mass of magnesium oxide that could form from this mass of magnesium is 4.05 g. Once cooled, the crucible actually contains 3.63 g of solid magnesium oxide.
(a)
What is the percentage yield of magnesium oxide in this experiment, to the nearest whole number?
[1 mark]
A111%
B68%
C90%
D40%
(b)
Which of the following is the most likely reason why the actual yield of magnesium oxide was less than the theoretical yield?
[1 mark]
AThe reaction between magnesium and oxygen is reversible, so some magnesium oxide broke back down into magnesium and oxygen gas as the crucible cooled
BThe relative formula mass of magnesium oxide used in the theoretical calculation was too high
CAll of the magnesium reacted completely to form magnesium oxide with no other substances formed and no losses at all
DSome of the magnesium oxide powder was lost from the crucible during heating and transfer, and/or some magnesium reacted with nitrogen in the air to form magnesium nitride instead of the oxide
(c)
Give the equation used to calculate percentage yield, and use it to explain why a percentage yield calculated from a real experiment can never be greater than 100%.
[2 marks]
Total for question 2: 4 marks
3
An industrial chemist running a Haber process plant is considering switching to a new, more active catalyst for converting nitrogen and hydrogen gas into ammonia, while keeping the temperature, pressure and the concentrations of the reactant gases exactly the same as before.
(a)
Write the balanced symbol equation, including state symbols, for the reaction between nitrogen and hydrogen in the Haber process, and state what is meant by describing this reaction as reversible.
[3 marks]
(b)
Predict and explain the effect of changing to the new, more active catalyst (with temperature, pressure and concentrations unchanged) on how quickly equilibrium is reached and on the equilibrium yield of ammonia obtained.
[4 marks]
Total for question 3: 7 marks
4
An off-grid weather monitoring station on a remote mountainside is powered by a hydrogen-oxygen fuel cell, housed inside a welded steel casing. The engineers are deciding whether to bolt a block of magnesium onto the outside of the steel casing, and are separately evaluating whether a fuel cell remains a suitable long-term power source for this hard-to-reach location.
(a)
Explain how the hydrogen-oxygen fuel cell produces a voltage, including the overall reaction taking place and the only product formed, and explain how this differs from a simple chemical cell (made from two different metals in an electrolyte), which produces a voltage only until one of its reactants is used up.
[6 marks]
(b)
Explain how bolting a block of magnesium to the outer surface of the steel casing would protect it from rusting by sacrificial protection, and evaluate whether a hydrogen fuel cell is a suitable power source for this remote weather station, compared with a simple sealed chemical cell, considering the practical challenges of its location.
[6 marks]
Total for question 4: 12 marks
5
An aerospace engineer compares pure aluminium with magnalium (an alloy of aluminium and magnesium) for use in aircraft wing panels, and separately compares pure copper with brass (an alloy of copper and zinc) for use in decorative door fittings.
(a)
Which statement correctly compares magnalium with pure aluminium?
[1 mark]
AMagnalium is softer than pure aluminium because alloying always weakens metallic bonding
BMagnalium conducts electricity less well than aluminium because alloying removes all delocalised electrons
CMagnalium is exactly as hard as pure aluminium because alloys have exactly the same structure as pure metals
DMagnalium is harder and stronger than pure aluminium because magnesium atoms, being a different size from aluminium atoms, distort the regular layers and make it harder for them to slide over each other
(b)
Brass is often used for decorative door fittings rather than pure copper. Which property makes brass more suitable for this use?
[1 mark]
ABrass is a pure element, so unlike copper it does not tarnish at all
BBrass is magnetic, unlike copper, which makes it easier to fix in place
CBrass is harder and more resistant to wear than pure copper, because zinc atoms distort the regular arrangement of copper atoms, while still keeping an attractive golden colour
DBrass conducts electricity much better than pure copper, which is essential for door fittings
(c)
Explain why gold used in jewellery is usually alloyed with other metals such as silver and copper, rather than being used in its pure form.
[2 marks]
Total for question 5: 4 marks
6
A pharmaceutical company synthesises a new drug in one step from an intermediate compound, X. In this step, 1 mole of X reacts to form 1 mole of the desired drug plus 1 mole of a useful by-product, Y, which is sold separately. The relative formula masses are: X = 180, drug = 150, Y = 28. In one batch, 90 kg of X is fully reacted.
(a)
What is the atom economy of this reaction for forming the desired drug, to the nearest whole number?
[1 mark]
A84%
B100%
C45%
D16%
(b)
What is the maximum (theoretical) mass of drug that could be produced from 90 kg of X?
[1 mark]
A90 kg
B75 kg
C62.5 kg
D100 kg
(c)
Explain why the company might prefer this reaction pathway over an alternative pathway that has a slightly higher percentage yield but a lower atom economy.
[2 marks]
Total for question 6: 4 marks
7
A fertiliser company produces ammonium nitrate on an industrial scale by continuously reacting ammonia gas with nitric acid in a large, cooled reactor. This is compared with a school laboratory method, in which a student neutralises a small volume of dilute nitric acid with ammonia solution using an indicator, before evaporating and crystallising the salt formed.
(a)
Write a balanced symbol equation for the reaction between ammonia and nitric acid, name the salt formed, and state why this salt is useful as a fertiliser.
[3 marks]
(b)
Explain one similarity and one difference between the school laboratory method and the industrial method of making an ammonium salt fertiliser, and explain why an indicator is needed in the school method but not in the industrial process.
[4 marks]
Total for question 7: 7 marks
8
A remote scientific research vessel is designing an emergency backup power system for use if its main generators fail at sea, and is choosing between a bank of simple zinc-carbon chemical cells and a hydrogen-oxygen fuel cell system.
(a)
Explain how a simple chemical cell, made from two different metals in an electrolyte, produces a voltage, and explain why its voltage falls and eventually stops.
[6 marks]
(b)
Evaluate whether the hydrogen-oxygen fuel cell system or the zinc-carbon chemical cell bank would be the more suitable emergency backup power source for this vessel, considering how long each can supply power, what supplies each would need, and any safety issues.
[6 marks]
Total for question 8: 12 marks

End of questions