Chemistry Form 5 Chapter 1

A substance is reduced if:

I. hydrogen is added

II. its oxidation number decreases

III. electrons are lost

IV. oxygen is lost

• I and II only

• II and IV only

• I, II and IV only

• All of the above

The reaction between chlorine water and potassium iodide solution may be represented by the ionic equation below:

Cl₂(aq) + 2I^-(aq) ---> 2Cl^-(aq) + I₂(aq)

Which of the following statements describes the reaction correctly?

I. Chlorine is the oxidising agent

II. Chlorine is more reactive than iodine

III. A reddish brown solution is formed

IV. The oxidation number of iodine increases

• I and II only

• II and III only

• I and IV only

• All of the above

Which equation does not represent a redox reaction?

• 2CuO(s) + C(s) ---> 2Cu(s) + CO₂(g)

• ZnO(s) + 2HCI(aq) ---> ZnCl₂(aq) + H₂O(I)

• CuSO₄(aq) + Zn(s) ---> Cu(s) + ZnSO₄(aq)

• 2Fe(s) + 3Cl₂(g) ---> 2FeCl₃(s)

Reactions occur when dry chlorine gas is passed through heated iron fillings. Which of the following describes the change in the reaction correctly?

I. Chlorine is molecules gains electrons

II. Iron is oxidised

III. White powder is formed

IV. Chlorine is the reducing agent

• I and II only

• II and IV only

• I, II and III only

• I, III and IV only

The table shows the results of reactions between different halogens and halide solutions.

The reactivity of halogens in ascending order is:

• bromine, chlorine, iodine

• bromine, iodine, chlorine

• iodine, bromine, chlorine

• chlorine, bromine, iodine

The figure shows the manufacture of sulphuric acid by the Contact process:

Which of the following describes he change in the oxidation number of sulphur correctly?

• 0 ---> -4 ---> +6 ---> -6

• 0 ---> +4 ---> +6 ---> +6

• +1 ---> +2 ---> +3 ---> +4

• +2--> +4 ---> +6 ---> +8

Which of the following represent oxidation?

I. Cl₂(g) ---> 2Cl^-(aq)

II. Fe²⁺(aq) ---> Fe³⁺(aq)

III. Mg(s) ---> Mg²⁺(aq)

IV. CuO(s) ---> Cu(s)

• I and III only

• II and III only

• I, II and III only

• I, II and IV only

In which of the following reactions are copper atoms ionised to form copper(II) ions?

• Copper in hot water

• Copper in dilute sulphuric acid

• Heated copper(II) oxide in hydrogen

• Copper in silver nitrate solution

Which of the following substances oxidise iodide ions to iodine?

I. Potassium chloride solution

II. Potassium bromide solution

III. Acidified potassium dichromate(VI) solution

IV. Acidified potassium manganate(VII) solution

• I and II only

• III and IV only

• I, II and III only

• All of the above

The figure shows the apparatus set-up for electron transfer at a distance in a redox reaction.

What could be Z?

• Bromine water

• Iron(III) sulphate solution

• Potassium iodide solution

• Acidified potassium dichromate(VI)