JAMB Chemistry Past Questions & Answers - Page 364

1,816.

When a crystal was added to the clear solution of its salt, the crystal did not dissolve and the solution remained unchange. This showed that the solution was

A.

supersaturated

B.

concentrated

C.

unsaturated

D.

saturated

Correct answer is D

No explanation has been provided for this answer.

1,817.

Water has the ability to dissolve almost all substance because its molecules has a structure with

A.

one positive end and one neutral end

B.

one positive end and one negative end

C.

two negative ends

D.

two positive ends

Correct answer is B

Water has partial positive and partial negative charges

1,818.

Which of the following results in the fall of acid rain?

A.

Oxides of lead

B.

Particulate matter

C.

Oxides of sulphur

D.

Gaseous hydrocarbon

Correct answer is C

No explanation has been provided for this answer.

1,819.

When 50cm2 of a saturated solution of sugar of molar mass 342 g at 40oC was evaporated to dryness, 34.2g of dry solid was obtained. The solubility of sugar at 40oC is

A.

2.0 mol dm-3

B.

3.5 mol dm-3

C.

7.0 mol dm-3

D.

10.0 mol dm-3

Correct answer is A

solubility = mole * 1000cm3/volume
mass/molar mass * 1000cm3/volume
= 34.2/342 * 1000cm3/50cm3-3

1,820.

The products of the combustion of candle wax are?

A.

hydrogen and water

B.

oxygen and water

C.

carbon (IV) oxide and water

D.

carbon (II) oxide and water

Correct answer is C

The heat of the flame vaporizes the liquid wax (turns it into a hot gas), and starts to break down the hydrocarbons into molecules of hydrogen and carbon. These vaporized molecules are drawn up into the flame, where they react with oxygen from the air to create heat, light, water vapor (H2O) and carbon dioxide (CO2).