WAEC Chemistry CBT Quiz

In the preparation of some pure crystals of Cu(NO3)2 starting with CuO, a student gave the following statements as steps he employed.

Liquid X, reacts with sodium trioxocarbonate (IV) (Na2CO3) to give a gas which turns calcium chloride solution milky. X is

An unknown organic compound X has a relative molecular mass of 180. It is a colourless crystalline solid, readily soluble in water. X contains the element C, H, and O in the atomic ratio 1:2:1. The compound has a sweet taste and melts on heating. In the presence of yeast and in the absence of air X is converted to compound Y in the absence of air, X is converted to compound Y and colourless gas. Compound Y reacts with sodium metal to produce a gas Z which gives a €˜pop€™ sound with a glowing splint. Y also reacts with ethanoic acid to give a sweet-smelling compound W.

An unknown organic compound X has a relative molecular mass of 180. It is a colourless crystalline solid, readily soluble in water. X contains the element C, H, and O in the atomic ratio 1:2:1. The compound has a sweet taste and melts on heating. In the presence of yeast and in the absence of air X is converted to compound Y in the absence of air, X is converted to compound Y and colourless gas. Compound Y reacts with sodium metal to produce a gas Z which gives a €˜pop€™ sound with a glowing splint. Y also reacts with ethanoic acid to give a sweet smelling compound W.

Which of the following pair of gases will NOT react further with oxygen at a temperature between 30°C and
400°C?

Solution X, Y, and Z have pH values 3.0, 5.0 and 9.0
respectively. Which of the following statements is
correct?

Some metals are extracted from their ores after some preliminary treatments by electrolysis (L) some by thermal reaction(T) and some bya combination of both processes(TL).