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

Question 21:

• JAMB 1981

The scale formation in a kinetic used for boiling water is caused by the presence in water of?

A. Calcium sulphate
B. Calcium carbonate
C. Calcium hydrogen carbonate
D. Calcium hydroxide
E. Magnesium sulphate

Question 22:

• JAMB 1982

When a pressure cooker is half filled with water, and heated to boiling point, then the pressure inside the cooker will?

A. Decrease, since only a fraction of the water molecules has changed to vapour
B. Remain constant, because the total number of water molecules has not changed
C. Increase, because the water molecules can now reach every part of the sealed tube
D. Decrease, since water boils under reduced pressure
E. Increase, because the water vapour molecules now strike the walls of the tube more frequently because of their increased velocity

Question 23:

• JAMB 1985

The boiling point of water, ethanol, toluene and butan-2-ol are 373.0k, 351.3k, 383.6k and 372.5k respectively. Which liquid has the highest vapour pressure at 323.0k?

A. Water
B. Toluene
C. Ethanol
D. Butan-2-ol
E. None

Question 24:

• JAMB 1985

In what respect will two dry samples of nitrogen gas differ from each other if sample 1 is prepared by completely removing CO₂ and O₂ from air, and sample 2 is prepared by passing purified nitrogen(i)oxide over heated copper? sample 1 is

A. Purer than sample 2
B. Slightly denser than sample 2
C. In all respects the same as sample 2
D. Colourless but sample 2 has a light brown colour
E. Slightly less reactive than sample 2

Question 25:

• JAMB 1986

Ammonia gas is normally dried with?

A. Concentrated sulphuric acid
B. Quicklime
C. Anhydrous calcium chloride
D. Magnesium sulphate