Question
This question is about iodine and compounds of iodine.
(a) Use the kinetic particle model to describe the separation between the molecules and the type of motion of the molecules in:
- solid iodine
- iodine gas. [4]
(b) The graph shows how the volume of iodine gas changes with pressure. The temperature is kept constant.
Describe how the volume of iodine gas changes with pressure.[1]
(c) (i) Complete the word equation to show the halogen and halide compound which react to form the products iodine and potassium bromide.
(ii) Explain, in terms of the reactivity of the halogens, why aqueous iodine does not react with aqueous potassium chloride
(d) lodine reacts with aqueous sodium thiosulfate, $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3$.
(i) Balance the chemical equation for this reaction.
$
\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3+\mathrm{I}_2 \rightarrow \mathrm{Na}_2 \mathrm{~S}_4 \mathrm{O}_6+\ldots . . \mathrm{NaI}
$
(ii) The energy level diagram for this reaction is shown.
Explain how this diagram shows that the reaction is exothermic [1]
(e) Describe a test for iodide ions.
test
observations[2]
(f) Molten sodium iodide is electrolysed.
Predict the product at the positive electrode.[1][Total: 14]
▶️Answer/Explanation
Ans:
(a) solid:
particles touching / particles close together (1)
particles (only) vibrating / not moving from place to place (1)
gas:
particles far apart (1)
particles moving fast / particles moving randomly / particles moving in any direction (1)
4(b) increasing the pressure decreases the volume / decreasing the pressure increases the volume / the higher the volume, the lower
the pressure
4(c)(i) bromine (1)
potassium iodide (1)
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 Group IV elements and their compounds.
(a) The changes of state of lead are shown.
Name the changes of state represented by A and B.[2]
A
B
(b) Use the kinetic particle model to describe the differences between liquid lead and lead gas in terms of:[4]
-
- the separation of the particles
- the motion of the particles.
(c) Lead is extracted from lead(II) oxide by heating with carbon.
PbO + C → Pb + CO
Describe how this equation shows that lead(II) oxide is reduced.[1]
(d) Lead is a pollutant of the air.
(i) State one source of lead in the air.[1]
(ii) State one adverse effect of lead on health.[1]
(e) Diamond is a form of carbon.
The structure of diamond is shown.
(i) Choose the word which best describes the structure of diamond.
Draw a circle around your chosen answer.[1]
giant ionic metallic simple
(ii) Name the type of bonding in diamond.[1]
(iii) Give one use of diamond.[1]
(iv) Deduce the electronic structure of carbon.
Use the Periodic Table to help you.[1] [Total: 13]
Answer/Explanation
Ans:
a) A: freezing (1)
B: boiling (1)
b) separation:
liquid: close together / some touching (1)
gas: far apart (1)
motion:
liquid: sliding over each other / restricted movement (1)
gas: moving freely (1)
(c) lead oxide has lost oxygen
(d)(i) (leaded) petrol / paints
(d)(ii) poisonous / toxic / harms nerves / harms brain
(e)(i) giant
(e)(ii) covalent
(e)(iii) cutting tools / for cutting / drill tips / jewelry
(e)(iv) 2,4