Question
This question is about iron and iron compounds.
(a) Name the main ore of iron. [1]
(b) In a blast furnace used for the extraction of iron, carbon reacts with oxygen from the air to form carbon monoxide.
Complete the chemical equation for this reaction.
$$
….. \rm{C}+\ldots \rightarrow2 \mathrm{CO}
$$ [2]
(c) In the hotter parts of the furnace, carbon reacts with the iron(III) oxide present in the iron ore.
$$
3 \mathrm{C}+\mathrm{Fe}_2 \mathrm{O}_3 \rightarrow 3 \mathrm{CO}+2 \mathrm{Fe}
$$
How does this equation show that carbon is oxidised? [1]
(d) Limestone is added to the blast furnace. The limestone is converted into calcium oxide and carbon dioxide. The reaction is endothermic.
$$
\mathrm{CaCO}_3 \stackrel{\text { heat }}{\longrightarrow} \mathrm{CaO}+\mathrm{CO}_2
$$
(i) What type of chemical reaction is this? [1]
(ii) What type of oxide is calcium oxide?
Give a reason for your answer. [2]
(e) Iron is a metal.
Give three physical properties that are characteristic of metals.
1……………………………………………
2…………………………………………
3 ……………………………………… [3]
(f) The structure of a compound of iron is shown.
Deduce the molecular formula of this compound to show the number of iron, carbon and oxygen atoms. [1]
▶️Answer/Explanation
Ans:
(a) hematite
(b) 2 (C) (1)
O2 (1)
(c) carbon gains oxygen (from Fe 2O3) / oxygen (from Fe 2O3) combines with carbon
(d)(i) thermal decomposition 1
(d)(ii) basic oxide (1)
calcium is a metal (oxide) (1)
(e) any three from:
• conduct electricity
• conduct heat
• malleable
• ductile
• shiny / lustrous
(f) $Fe_{2}C_{9}O_{9}$
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 metals.
(a) State three general physical properties common to most metals.[3]
1
2
3
(b) Metals are often used in the form of alloys.
(i) State the meaning of the term alloy.[1]
(ii) Explain in terms of their properties why alloys are used instead of pure metals.[1]
(iii) Stainless steel is an alloy.
Give one use of stainless steel.[1]
(c) Place these metals in order of their reactivity with oxygen.
copper
magnesium
potassium
zinc
Put the least reactive metal first.[2]
(d) When 4.8g of magnesium reacts with excess oxygen, 8.0g of magnesium oxide is formed.
Calculate the minimum mass of magnesium needed to produce 24.0g of magnesium oxide.
minimum mass = g [1] [Total: 9]
Answer/Explanation
Ans:
a) 1 mark each for any three of:
-
- conduct electricity / conduct heat
- malleable
- ductile
- shiny / lustrous
- sonorous / rings when hit
(b)(i) mixture of metal with another element
(b)(ii) (alloy is) hard(er) / (more) resistant to corrosion / strong(er)
(b)(iii) cutlery / chemical plant / surgical equipment
(c) copper , zinc , magnesium , potassium (2)
if 2 marks not scored: 1 mark for one consecutive pair reversed
(d) 14.4 (g)