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
Some elements are shown in the order they appear in the reactivity series. The most reactive element is at the top.
sodium
calcium
magnesium
aluminium
zinc
iron
hydrogen
copper
(a) Answer the questions using the list of elements. Each element may be used once, more than once or not at all.
Identify:
(i) a non-metal
(ii) a metal which is stored under oil
(iii) the main component of steel
(iv) a metal with three electrons in the outer shell of its atoms
(v) a metal found in brass
(vi) a metal that forms chlorides of the type \(XCl_2\) and \(XCl_3\).
(b) Name the main ores of:
(i) zinc ……………………………………………………………………………………………………………….
(ii) aluminium. ……………………………………………………………………………………………………..
(c) In an experiment, a sample of aluminium appeared less reactive than expected.
Explain why.
(d) Name two metals from the list which are extracted by reduction of their ores using carbon.
1 ……………………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………………….
(e) When zinc granules are added to aqueous copper(II) sulfate, a reaction occurs. During the
reaction, a red-pink solid is formed and the solution becomes colourless.
(i) Name the red-pink solid.
(ii) Name the colourless solution.
(iii) Explain, in terms of particles, why the rate of this reaction increases when the temperature
is increased.
(iv) Suggest two other ways of increasing the rate of this reaction.
1 …………………………………………………………………………………………………………………………
2 …………………………………………………………………………………………………………………………
Answer/Explanation
Answer:
(a) (i) hydrogen
(ii) sodium
(iii) iron
(iv) aluminium
(v) zinc or copper
(vi) iron
(b) (i) zinc blende
(ii) bauxite
(c) protective oxide layer
(d) Any 2 from 3
• zinc
• iron
• copper
(e) (i) copper
(ii) zinc sulfate
(iii)
M1 particles have more energy
M2 More collisions (between particles) occur per second / per unit time
M3 A greater percentage / proportion / fraction of collisions (of particles) are successful / have energy above activation
energy / have energy equal to activation energy
(iv) Any 2 from 3:
• use a catalyst
• use smaller granules
• increase concentration
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