WAEC Chemistry Past Questions

25cm3 of a gas X contains Zmolecules at 150C and 75mmHg. How many molecules will 25cmm3 of another gas Y contain at the same temperature and pressure

1. a.2Y
2. b.2Z
3. c.Z
4. d.Y

The pollution from petroleum spillage in rivers and lakes can best be dispersed by

1. a.Pouring detergents
2. b.Passing of ships through the area
3. c.Pouring organic solvents
4. d.Evaporation

In the electrolysis of a concentrated solution of sodium chloride using inert electrodes, which of the following ions are discharged at the cathode and anode respectively

1. a.Na+ and Cl-
2. b.Na+ and OH-
3. c.H+ and OH-
4. d.H+ and Cl-

CO(g) + H2O(g) ⇌ CO2(g) + H2(g) From the reaction above, calculate the standard heat change if the standard enthalpies of formation of CO2 (g), H2O (g) and CO (g) in kJ mol-1 are -394, -242 and -110 respectively.

1. a.-262 kJ mol-1
2. b.-42kJ mol-1
3. c.+42 kJ mol-1
4. d.+262 kJ mol-1

When sugar is dissolved in tea, the reaction is always accompanied by

1. a.Positive entropy change
2. b.Negative entropy change
3. c.No entropy change
4. d.A minimum entropy change

Which of the following is an electrolyte

1. a.Alcohol
2. b.Sodium acetate solution
3. c.Solid potassium hydroxide
4. d.Mercury

Chlorine gas is prepared in the laboratory by

1. a.Adding concentrated hydrochloric acid to solid manganese (IV) oxide
2. b.Adding concentrated tetraoxosulphate (VI) acid to solid sodium chloride
3. c.Dropping concentrated hydrochloric acid onto potassium tetraoxomanganate (VII) crystals
4. d.Oxidizing concentrated hydrochloric acid using potassium heptaoxodichromate (VI) crystals

Metals of the first transition series have special proper ties which are different from those of groups I and II elements because they have partially filled

1. a.s orbitals
2. b.p orbitals
3. c.d orbitals
4. d.f orbitals