Chemistry Past Questions and Answers

In which of the following reactions does hydrogen peroxide act as a reducing agent?

A H₂S + H₂O₂ \(\to\) S + 2H₂O
B PbSO₃ + H₂O₂ \(\to\) PbSO₄ + H₂O
C 2I+ 2H⁺ + H₂O₂ \(\to\) I₂ + 2H₂O
D PbO₂ + 2HNO₃ + H₂O₂ \(\to\) Pb(NO₃)₂ + 2H₂O + O₂
E SO₂ + H₂O₂ \(\to\) H₂SO₄

Question 12:

For the reaction 2Fe³⁺ 2I^- \(\to\) 2Fe²⁺ + I₂, which of the following statements is TRUE?

A Fe is oxidized to Fe³⁺
B Fe³⁺ is oxidized to Fe²⁺
C I^- is oxidized to I₂
D I^- is reduced to I₂
E I^- is displacing an electron from Fe³⁺

Question 13:

In dilute solution the heat of the reaction NaOH + HCl = NaCl + H2O is - 57.3kJ. Therefore the heat of the reaction 2NaOH + H₂SO₄ \(\to\) Na₂SO₄ + 2H₂O is

A + 28.65 kJ
B - 28.65KJ
C + 57.3KJ
D - 114.6 KJ
E - 229.2 KJ

Question 14:

Which of the following methods may be used to prepare trioxonitrate (V) acid (nitric acid) in the laboratory?

A Heating ammonia gas with tetraoxosulphate (VI) acid
B Heating ammonium trioxonitrate (V) with tetraoxosulphate (VI) acid
C Heating sodium trioxonitrate (V) with tetraoxosulphate (VI) acid
D Heating potassium trioxonitrate (V) with calcium hydroxide
E Heating a mixture of ammonia gas and oxygen.

Question 15:

Lime - water, which is used in the laboratory for the detection of carbon(iv)oxide is an aqueous solution of

A Ca(OH)₂
B CaCO₃
C CaHCO₃
D CaSO₄
E N₂CO₃