Question
The Periodic Table can be used to classify elements.
(a) Group I elements react with cold water to form alkaline solutions.
(i) Place the Group I elements caesium, lithium, potassium, rubidium and sodium in their order of reactivity with water.
Put the most reactive element first. [1]
(ii) Name the alkaline solution formed when caesium reacts with cold water.[1]
(b) Group I elements have lower melting points than transition elements.
Describe one other difference in the physical properties of Group I elements and transition elements.[1]
(c) Group VII elements are known as the halogens.
Astatine is below iodine in Group VII.
Predict the physical state of astatine at room temperature and pressure.[1]
(d) Some Group VII elements react with aqueous solutions containing halide ions.
When aqueous chlorine is added to aqueous potassium bromide a reaction occurs.
The ionic half-equations for the reaction are shown.
Cl2(aq) + 2e– → 2Cl– (aq)
2Br– (aq) → Br2(aq) + 2e–
(i) Describe the colour change of the solution. [2]
original colour of potassium bromide solution
final colour of reaction mixture
(ii) Identify the species that is oxidised.
Explain your decision.[2]
species oxidised
explanation
(e) Bromine monochloride, BrCl, is made by the reaction between bromine and chlorine. The chemical equation is shown.
Br2(g) + Cl2(g) → 2BrCl(g)
Calculate the overall energy change for the reaction using bond energies.
Use the following steps.
-
- Calculate the total amount of energy required to break the bonds in 1 mole of Br2(g) and 1 mole of Cl2(g).
kJ
-
- Calculate the total amount of energy released when the bonds in 2moles of BrCl(g) are formed.
kJ
-
- Calculate the overall energy change for the reaction.
kJ/mol
[3] [Total: 11]
Answer/Explanation
Ans:
7(a)(i) from left to right
caesium → rubidium → potassium →sodium → lithium
7(a)(ii) caesium hydroxide
7(b) Group I element is less strong / not strong
ORA
OR
Group I element has low(er) density ORA
OR
Group I element is soft(er) ORA
7(c) solid
7(d)(i) colourless (1)
orange / brown / yellow (1)
7(d)(ii) Br– (1)
loses electron(s) (1)
7(e) 432(1)
436(1)
– 4(1)
Question
This question is about iron.
(a) Iron is extracted from its main ore in a blast furnace.
(i) Name the main ore of iron used in the blast furnace.
(ii) Name the substance that enters the blast furnace at A.
(iii) Name the substance that leaves the blast furnace at B.
(iv) Give two reasons for using coke in the blast furnace.
1 …………………………………………………………………………………………………………………………
2 …………………………………………………………………………………………………………………………
(b) Another ore of iron is iron pyrites, \(FeS_2\). Iron pyrites contains the positive ion, \(Fe^{2+}\).
Deduce the formula of the negative ion in \(FeS_2\).
(c) Iron is a transition element.
A list of properties of iron is shown.
● Iron is a good conductor of electricity.
● Iron forms soluble salts.
● Iron forms coloured compounds.
● Iron has variable oxidation states.
● Iron acts as a catalyst.
● Iron forms a basic oxide.
(i) Give two properties from the list in which iron differs from Group I elements.
1 …………………………………………………………………………………………………………………………
2 …………………………………………………………………………………………………………………………
(ii) Give two properties from the list in which iron is similar to Group I elements.
1 …………………………………………………………………………………………………………………………
2 …………………………………………………………………………………………………………………………
(d) Steel consists mainly of iron.
Iron forms rust when it reacts with water and oxygen.
Magnesium blocks can be attached to the bottom of steel boats. The magnesium does not
completely cover the steel.
(i) Explain how the magnesium blocks prevent iron from rusting.
(ii) Explain why replacing the magnesium blocks with copper blocks will not prevent the
bottom of the boat from rusting.
Answer/Explanation
Answer:
(a) (i) hematite
(ii) air
(iii) slag / calcium silicate
(iv) any two from:
• (coke)
releases heat (when it reacts with oxygen or reacts in air)
OR (acts as a) fuel
OR increases temperature (in the furnace) / heats (the furnace)
OR source of energy
• (coke or carbon monoxide)
reduces iron oxide
OR is a reducing agent
OR converts iron oxide to iron /
removes oxygen from iron oxide
• (coke)
reacts with oxygen to form carbon monoxide
OR reacts with carbon dioxide to form carbon monoxide
(b) \(S_2^{2-}\) or S-
(c) (i) any two from:
• (iron forms) coloured compounds
• (iron has) variable oxidation states
• (iron acts as a) catalyst
(ii) any two from:
• (iron is) good conductor of electricity
• (iron) forms a basic oxide
• (iron salts are) soluble (in water)
(d) (i) magnesium is more reactive than iron / steel ORA (1)
iron is not oxidised
OR
iron does not lose electrons
OR
magnesium loses electrons more easily than or in preference (to iron) ORA
OR
magnesium is oxidised more easily or reacts with oxygen more easily or corrodes more easily or in preference (to iron)
ORA (1)
(ii) copper is less reactive than iron / copper is lower in the reactivity series than iron ORA
Question
This question is about transition elements.
(a) Transition elements are harder and stronger than Group I elements.
Describe two other differences in physical properties between transition elements and Group I elements.[2]
1
2
(b) State one physical property of transition elements that is similar to Group I elements.[1]
(c) State two chemical properties of transition elements.[2]
1
2
(d) Cobalt is a transition element. Anhydrous cobalt(II) chloride is used to test for water.
State the colour change that occurs when water is added to anhydrous cobalt(II) chloride. from ________ to ________ [2]
(e) Iron is a transition element.
(i) Which two substances react with iron to form rust?[2]
1
2
(ii) Which metal is used to galvanize iron?[1]
(f) The hull of a ship is made from steel (mainly iron). Metal blocks are placed on the ship’s hull to prevent rusting.
Use your knowledge of the reactivity series to explain why:
-
- magnesium is suitable to use as the metal blocks
- copper is not suitable to use as the metal blocks.[2]
(g) Rust contains iron(III) oxide.
Phosphoric acid, H3PO4, can be used to remove rust from an iron object and prevent further rusting.
(i) Write a chemical equation for the reaction between iron(III) oxide and phosphoric acid to form iron(III) phosphate and water.[2]
(ii) Iron(III) phosphate is an insoluble salt.
Suggest how the formation of iron(III) phosphate prevents further rusting.[1] [Total: 15]
Answer/Explanation
Ans:
6(a) M1 Transition element has higher melting point / high boiling point ORA(1)
M2 Transition element has higher density ORA(1)
6(b) good conduction of heat or electricity OR malleability OR ductility
6(c) 1 mark each for any two of:
-
- catalyst
- more than one or different or variable oxidation state / oxidation number / valency
- coloured compounds / coloured ions
6(d) from blue(1) to pink(1)
6(e)(i) M1 oxygen(1)
M2 water(1)
6(e)(ii) zinc / Zn 1
6(f) M1 magnesium above iron / steel in the reactivity series ORA / magnesium more reactive than iron / steel ORA(1)
M2 copper below iron / steel in the reactivity series ORA / copper less reactive than iron ORA(1)
6(g)(i) Fe2O3 + 2H3PO4 → 2FePO4 + 3H2O
M1 FePO4 anywhere(1) M2 The whole equation correct(1)
6(g)(ii) iron(III) phosphate acts as a barrier which prevents contact between iron and water or air / oxygen