Question
This question is about copper and copper compounds.
(a) Describe how you could prepare a pure sample of crystals of hydrated copper(II) sulfate using dilute sulfuric acid and an excess of copper(II) oxide.[3]
(b) Anhydrous copper(II) sulfate is used to test for water.
(b) Anhydrous copper(II) sulfate is used to test for water.
$
\begin{aligned}
& \mathrm{CuSO}_4+5 \mathrm{H}_2 \mathrm{O} \rightleftharpoons \mathrm{CuSO}_4 \cdot 5 \mathrm{H}_2 \mathrm{O} \\
& \text { anhydrous hydrated } \\
& \text { copper(II) sulfate copper(II) sulfate } \\
&
\end{aligned}
$
(i) What is meant by the symbol $\rightleftharpoons$ ?[1]
(ii) How can hydrated copper(II) sulfate be changed into anhydrous copper(II) sulfate?[1]
(c) Complete the table to calculate the relative formula mass of anhydrous copper(II) sulfate, $\mathrm{CuSO}_4$. Use your Periodic Table to help you.
relative formula mass = …………………………. [2]
(d) Complete the table to show the number of electrons, protons and neutrons in the sulfur atom and copper ion shown.
(e) Alloys of copper are used to make coins.
(i) What is meant by the term alloy?[1]
(ii) Suggest why an alloy of copper is used to make coins instead of using pure copper.[1] [Total: 13]
▶️Answer/Explanation
Ans:
a) any three from:
• heat copper oxide with sulfuric acid
• filter off (excess) copper oxide
• heat filtrate to point of crystallisation / heat (copper sulfate) solution to point of crystallisation
• dry between filter papers / dry in drying oven
(b)(i) reversible reaction 1
(b)(ii) heat / warm 1
(c) 160 (2 marks)
if 2 marks not scored 1 mark for S = (1 × 32) = 32 OR O (= 4 × 16) = 64
(d) electrons in S = 16 (1)
electrons in Cu 2+ = 27 (1)
neutrons in S = 18 AND neutrons in Cu 2+ = 34 (1)
protons in S = 16 (1)
(e)(i) mixture of metal and other elements 1
(e)(ii) (alloy) more resistant to wear / stronger / harder / more resistant to corrosion ORA for copper
Question
This question is about zinc and compounds of zinc.
(a) Zinc is a metal.
Give three physical properties of metals.[3]
1
2
3
(b) Zinc reacts with phosphorus to form zinc phosphide, Zn3P2.
Complete the equation for this reaction.[2]
Zn + P → Zn3P2
(c) Molten zinc chloride is electrolyzed.
The incomplete apparatus is shown.
(i) Complete the diagram by:[2]
completing the circuit to show the wires and power pack
labelling the anode.
(ii) Name the products formed at each electrode.[2]
positive electrode
negative electrode
(d) Zinc chloride reacts with water as shown. The solution formed is acidic.
\(ZnCl_{2}+2H_{2}O\rightleftharpoons Zn\left ( OH \right )_{2}+2HCl\)
(i) State the meaning \(\rightleftharpoons\) of the symbol .[1]
(ii) Choose the pH value which is acidic.
Draw a circle around your chosen answer.[1]
pH 3 pH 7 pH 9 pH 14
(e) A compound of zinc has the formula ZnC4H10.
Complete the table to calculate the relative molecular mass of ZnC4H10.
relative molecular mass = [2] [Total: 13]
Answer/Explanation
Ans:
(a) 1 mark each for any three of:
-
- conduct electricity OR conduct heat (1)
- malleable (1)
- ductile (1)
- shiny / lustrous (1)
(b) 3 (Zn) (1)
2 (P) (1)
(c)(i) wires leading from each side of power pack or battery to the electrodes (1)
positive electrode labelled anode (1)
(c)(ii) positive electrode: chlorine (1)
negative electrode: zinc (1)
d)(i) reversible reaction
(d)(ii) pH 3
(e) 123 (2)
if two marks not scored, allow 1 mark for C = 4 x 12 / 48 OR H = 1 x 10 / 10
Question
This question is about elements in the Periodic Table.
(a) The table shows some properties of five elements, P, Q, R, S and T.
Use only the elements shown in the table to answer this question.
State which two of the elements, P, Q, R, S and T, are covalent molecules.
Give two reasons for your answer.
elements …………………………………………………….. and ……………………………………………………..
reason 1 …………………………………………………………………………………………………………………….
reason 2 …………………………………………………………………………………………………………………….
(b) Element T is on the left-hand side of the Periodic Table.
Suggest whether its oxide is acidic or basic.
Give a reason for your answer.
(c) Krypton is an element in Group VIII of the Periodic Table.
Explain, using ideas about electronic structure, why krypton is unreactive.
(d) Sodium is an element in Group I of the Periodic Table. Iron is a transition element.
Iron has a higher melting point and higher boiling point than sodium.
Give two other ways in which the properties of transition elements differ from the properties of
Group I elements.
1 ……………………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………………….
(e) The table compares the reactivity of four metals with dilute hydrochloric acid.
Put the four metals in order of their reactivity.
Put the least reactive metal first.
(f) Hot iron reacts with steam. The reaction is reversible.
Complete the equation by writing the symbol for a reversible reaction in the box.
(g) Steel is an alloy of iron.
State the meaning of the term alloy.
Answer/Explanation
Answer:
(a) Q AND S (1)
low melting points (1)
poor conductor (of electricity) / does not conduct (electricity) (1)
(b) basic (oxide) AND
T is a metal / metal oxides are basic
(c) has a complete outer (electron) shell / has a full outer (electron) shell
(d) 1 mark each for any 2 of:
• transition elements have a high(er) density / Group I has a low(er) density
• transition elements form coloured compounds / Group I compounds are not coloured
• transition elements form ions with different charges / Group I forms only one type of ion
• transition elements are good catalysts / Group I elements not catalysts
(e) copper < nickel < iron < calcium (2)
if 2 marks not scored, 1 mark for:
1 consecutive pair reversed / calcium < iron < nickel < copper
(f) \(\leftrightarrow \)
(g) mixture of metal with another element