JAMB Chemistry Past Questions & Answers - Page 35

171.

When a solid substance disappears completely as a gas on heating, the substance is said to have undergone?

A.

Sublimation

B.

Crystallization

C.

Distillation

D.

Evaporation

Correct answer is A

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state.

172.

When cathode rays are deflected onto the electrode of an electrometer, the instrument becomes?

A.

Bipolar

B.

Negatively charged

C.

Positively charged

D.

Neutral

Correct answer is B

When these cathode rays are deflected onto an electrode of an electrometer, the instrument measured a negative charge. The rays tested also were deflected by application of an electric field.

173.

The general formula for the Alkanals is?

A.

R\(_2\)CO

B.

RCHO

C.

ROH

D.

RCOOR

Correct answer is B

Alkanals or Aldehydes have the general formula RCHO while Alkanones or Ketones have the general formula RCOR'.

Where R and R' may be alkyl or aryl groups.

174.

Proteins in acid solution undergo?

A.

Substitution

B.

Fermentation

C.

Hydrolysis

D.

Polymerisation

Correct answer is C

Acid hydrolysis refers to a hydrolysis reaction occurring under acidic conditions. Acid hydrolysis of a protein breaks the polymer down into its constituent amino acids.

175.

What mass of water is produced when 8.0g of hydrogen reacts with excess oxygen?

A.

8.0g

B.

16.0g

C.

36.0g

D.

72.0g

Correct answer is D

2H\(_2\) + O\(_2\)  ⇒ 2H\(_2\)O

From the equation:

4g of Hydrogen produces 36g of water

: 8g of Hydrogen will produce 72g of water