WAEC GCE Chemistry Questions and Answers 2019/2020 | WAEC OBJ & Theory Answers

(1b)
(i) Sand bed: It is used as a filtration step in treatment of river water.
(ii) Chlorine: It is used as disinfectant (kills germs) in the treatment of water.
(iii) Alum: It is used in the coagulation of dirt particles in a sample of water.

(1c)
(i) The number of particles.
(ii) The energy of the reacting or colliding particles.

(1d)
Palm wine turns sour after some days due to the fermentation of glucose to alcohol through the process known as fermentation, which further oxidation turns to ethanoic acid.

(1e)
(i) Acids react with metals to form salt and hydrogen gas liberated.
(ii) They react with bases to form salt and water.
.
(1f)
(i) electroplating of the metal.
(ii) the use of alloy.

(1g)
(i) Be
(ii) Li and F

(1h)
Pv = nRT
R = Pv/nT
= 1.0132 × 10^5 × 22.4/1 × 273.14
= 8309.17dm³Nm-²mol- k-

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.
(3ai)
Structural formula is one which shows the araangemt of atoms in the molecules.

(3aiï)
Draw the hydrocarbon

(3aiii)
Pentane; 2-methylbutane; 2,2-dimethyl propane.

(3bi)
(i) He observed that alpha particles scattered at varying degrees.
(ii) A visible flash of light was produced.
.
(3bii)
That atom consists of a positive core called nucleus, where most of the mass of the atom is contained and electrons which move around the nucleus.

(3ci)
(i) Law of conservation of mass : It states that matter is neither created nor destroyed during chemical reaction but changes from one form to another.

(ii) Law of definite proportions : It states that all pure samples of a particular chemical compound contain silver elements combined in the same proportion by mass.

(3cii)
(i) Temperature
(ii) Presence of oxygen
(iii) The solubility capacity of the ionic solid
.

(3ciii)
CO2 is gas but SiO2 is solid because the SiO2 is in giant molecul