JAMB Chemistry Past Questions & Answers - Page 150

747.

Increasing the pressure of a gas

A.

lowers the average kinetic energy of the molecules

B.

decreases the density of the gas

C.

decreases the temperature of the gas

D.

increases the density of the gas

E.

increases the volume of the gas

Correct answer is D

No explanation has been provided for this answer.

748.

Which of the following separation processes is most likely to yield high quality ethanol (>95%) from palm wine?

A.

Fractional distillation without a dehydrant

B.

simple distillation with a dehydrant

C.

fractional distillation with a dehydrant

D.

column chromatography

E.

evaporation

Correct answer is C

Fractional distillation with a dehydrant is the most likely separation process to yield high-quality ethanol from palm wine. Adding a dehydrant helps to remove water from the ethanol more effectively during the distillation process, resulting in a higher purity of ethanol. This is important for producing high-quality ethanol suitable for various applications, including consumption or industrial use.

749.

In the preparation of some pure crystals of Cu (NO3)2 starting with CuO, a student gave the following statements as steps he employed. Which of these shows a flaw in his report ?

A.

some CuO was reacted with excess dilute H2SO4

B.

the solution was concentrated

C.

when the concentrate was cooled, crystals formed were removed by filtration

D.

the crystals were washed with very little cold water

E.

the crystals were then allowed to dry

Correct answer is A

No explanation has been provided for this answer.

750.

Some metals are extracted from their ores after some preliminary treatments by electrolysis (L), some of both processes (TL). Which set-up in the following for the extraction of ion, copper and aluminium is correct?

A.

lron (L), copper (L) aluminium (T)

B.

lron (T) copper (L) aluminium (T)

C.

lron (TL) copper (TL) aluminium (TL)

D.

Iron (L) copper (T) aluminium (T)

E.

lron (T) copper (L), aluminium (TL)

Correct answer is E

No explanation has been provided for this answer.