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WAEC GCE 2020: Jan/Feb Chemistry Alternative To Practcal Solutions

(2)
TABULATE Test | Observation | Inference

(i)
TEST:
Sample C + water 5cm^3 of C + NaoH in drop and in excess |

OBSERVATION:
soluble white gelatinous precipitate in drop. White soluble or dissolve (in excess).

INFERENCE:
Soluble salt. Zn^2+ or Al^3+ present.

(ii)
TEST:
5cm^3 of C + NH4OH in drop, then in excess.

OBSERVATION:
white gelatinous precipitate in drop. White gelatinous ppt dissolve in excess.

INFERENCE:
Zn^2+ or Al^3+ present. Zn^2+ confirmed (in excess).

(iii)
TEST:
Solution of sample C + dilute HN3 + BaCl2(aq) + HCl(aq)

OBSERVATION:
No visible reaction. White ppt form. White ppt insoluble in dilute Hcl.

INFERENCE:
SO3^2- or SO4^2- may be present. SO4^2- confirmed.

(iv)
TEST:
Sample D + dilute Hcl(aq)

OBSERVATION:
A colourless and odourless gas evolve with a effervescence. The gas turn like water milky. The gas turn blue litmus to red.

INFERENCE:
The gas in CO2 from CO3^2- or HCO3-

Updated: January 23, 2020 — 5:02 pm

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