IGCSE CHEMISTRY Test on Metals

IGCSE CHEMISTRY Test on Metals

Q.1 Zinc and copper are elements next to each other in the Periodic Table.

(a) Zinc is obtained from zinc blende in a two-step process.

Outline how each of these steps are done.

step 1

Roasting of zinc blende (in oxygen)
2ZnS + 3O2 → 2ZnO + 2SO2

step 2

Reaction with coke
ZnO + C → Zn + CO OR 2ZnO + C → 2Zn + CO2

removal of zinc in step 2

Molten zinc is removed by distillation. [5]

(b) Name the alloy formed when zinc is mixed with copper.

Brass.[1]

(c) Copper is a transition element. It can have variable oxidation states.

State two other chemical properties of transition elements which make them different from

Group I elements.

Transition elements form coloured compounds / ions (1)
They act as catalysts (1)

(d) A compound of copper can be used to test for water.

(i) State the full name of this compound of copper.

anhydrous copper(II) sulfate or Hydrated copper sulfate [1]

(ii) State the colour change that occurs when water is added to this compound of copper.

anhydrous copper(II) sulfate – white to Blue

Or Hydrated copper sulfate – Blue to white[2]

(e) Aqueous potassium iodide reacts with aqueous copper(II) sulfate to produce iodine.

(i) Balance the chemical equation for this reaction.

4KI + 2CuSO4 → 2CuI + I2 + 2K2SO4                          [2]

(ii) Deduce the charge on the copper ion in CuI.

1+ [1]

(iii) In terms of electron transfer, explain why copper is reduced in this reaction.

Cu2+ changed to Cu+ means gains electron [1]

(iv) Identify the reducing agent.

KI / potassium iodide / iodide (ions) / I–[1]

This question is about iron and iron compounds.

Q 2. (a) Name the main ore of iron.

Haematite [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.

2C + O2 –>2CO    [2]

(c) In the hotter parts of the furnace, carbon reacts with the iron(III) oxide present in the iron ore.

3C + Fe2O3—> 3CO + 2Fe

How does this equation show that carbon is oxidised?

Carbon gains oxygen and also oxidation state of carbon changes from 0 to 2

(d) Limestone is added to the blast furnace. The limestone is converted into calcium oxide and

carbon dioxide. The reaction is endothermic.

CaCO3 —-> CaO + CO2

(i) What type of chemical reaction is this?

Thermal decomposition [1]

(ii) What type of oxide is calcium oxide?

Give a reason for your answer.

Calcium oxide is a basic oxide because calcium is a metal of 2nd group and metal oxides are basic in nature because they form base.

(e) Iron is a metal.

Give three physical properties that are characteristic of metals.

Malleable/ductile

High MP/BP

Good conductor of heat and electricity

Q 3. Aluminium is extracted from aluminium oxide by electrolysis.

(a) Why is aluminium not extracted by heating aluminium oxide with carbon?

Aluminium is more reactive than carbon so carbon can not reduce Aluminium oxide to aluminium.( reactivity series)

(b) Aluminium oxide is an ionic compound with a high melting point.

(i) Complete the dot-and-cross diagram to show the electron arrangement in one of the oxide ions present in aluminium oxide. Include the charge on the oxide ion.

Oxide ion with electrons

(ii) The melting point of aluminium oxide is above 2000 °C. Explain why aluminium oxide has a high melting point.

Due to strong electrostatic force of attraction between Al ions and oxide ions.

(c) Aluminium can be extracted by electrolysis

(i) Name the type of particle responsible for the transfer of charge in

the wires,

Electrons

the electrolyte.

Ions

(ii) Give two reasons why cryolite is used.

To reduce the MP

To lower the cost

To increase the electrical conductivity

(iii) Write the ionic half-equation for the formation of aluminium during the electrolysis.

Al3+ +3e —> Al

(iv) Explain how carbon dioxide gas is formed at the anodes.

Oxygen gas is formed at anode which reacts with graphite anode and forms CO2.

Test-on-Metals-grade-11

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