Separation of mixtures and purification of chemical substances - Jamb Chemistry Past Questions and Answers

Question 11:

• JAMB 1979

If chlorine gas is bubbled into water and then this yellowish-green coloured solution is exposed to bright sunlight for a while

A. The solution will give out chlorine gas and hydrogen chloried gas
B. The solution will produce chlorine gas and oxygen
C. The solution will give out solution will producing hypochloric acid
D. The solution is decomposed giving out oxygen, hydrogen and chlorine
E. The solution will give out oxygen gas leaving behind aqueous hydrochloric acid

Question 12:

• JAMB 1979

When a piece of charcoal enclosed in a cylinder containing air is ignited

A. The toatl volume of air is increased
B. The relative amount of oxygen present is increased
C. The relative amount of nitrogen present is decreased
D. The relative amount of carbondioxide present is increased
E. The ratio of oxygen to nitrogen in the system is increased

Question 13:

• JAMB 1979

Weighed salts Y and Z were left exposed in the laboratory overnight. In the morning Y had gained weight, and Z had become liquid. What conclusion could be drawn about the nature of the two salts?

A. Z is efflorescent
B. Y and Z are efflorescent
C. Y and Z are deliquescent
D. Y and Z are hygroscopic
E. Y is deliquescent

Question 14:

• JAMB 1979

In the manufacture of iron in the blast furnace, iron (lll) oxide is mixed with coke and limestone, and different reactions occur in the process. Which of the following statements is true with respect to these reactions?

A. The coke is a powerful reducing agent and easily converts the iron oxide to iron
B. The calcuim carbonate reacts with SiO₂ an earthly impurity in the ore, to from calcuim silicate
C. The coke will react with the iron produced to form steel
D. All the carbondioxide required in the process comes from the decomposition of the calcium carbonate
E. The calcium carbonate decomposes to give calcium oxide, which then forms calcium silicate with the earthly impurity

Question 15:

• JAMB 1979

One of the following techniques can be used to show that chlorophyll pigment is a mixture of chemical compounds and not a single coloured compound

A. Cystallization
B. Hydrolysis
C. Sublimation
D. Filtration
E. Chromatography