WAEC 2013 GCE Alternative to Chemistry Practical Question and Answers

(1a) Va=22.50cm3,
mass conc. Of acid(Ca)=mass conc/molar mass,

molar mass NaHSO4=23+1+32+64=120g/mol ,

molar conc Ca=10.6/120=0.0883mol/dm3

(1aii)Cb=(0.0883*22.50)/25=0.0795mol/dm3 
(1aiii)mass conc. Cb=0.0795*40=3.178g/dm3,
X=3.178g/dm3

(1aiv) n=C*V/1000,
n of Na2SO4=mass/molar mass,
nb=(0.0795*25)/1000=0.0019875,
mass of NaSO4=n*molar mass,mass of Na2SO4=142g/mol,
mass of Na2SO4=0.0019875*142=0.282g.

(1bi) Phenopthalein
1bii)  (I.) Burette (II) Pipette

(2a)observation: Did not dissolve.
Inference: D is insoluble in water.

(2b) observation : dissolves to form blue or greenish solution.

Inference: D contains Cu2+ or Fe2+ ions

(2c) observation:blue gelatinous ppt.
Inference: Cu2+ is present.

 (2d)observation: blue ppt.,ppt dissolves to form a dip-blue solution.

Inference: Cu2+ confirmed

(3aii) Voltameter
(3aiii)
I. Acidified water
II. Alcohol

(3b)
i.  Kip’s apparatus
ii.  Solubility Can

(3ci)
i. Ammonia Solution (NH3H2O)
ii. Sodium Hydroxide Solution (NaoH)

(3cii)
i. Pb^2+, Zn^2+, Al3+ give a white gelatinous ppt with NaoH solution, soluble in excess
ii. Ca^2+ gives a dirty White ppt, Insoluble in excess of NaoH and Ammonia

iii. Pb^2+  and Al^3+ give white gelationous ppt, insoluble in excess Ammonia Solution

(3d) End point -It means the point at which the acid solution exactly neutralizes the given volume of base at end point(H+)=(OH)