Chemistry questions and answers

Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

381.

Consider the following reaction equation: 2Al(OH)\(_3\) + 3H\(_2\)SO\(_4\) Al\(_2\)(SO4)\(_3\)(aq)+6H\(_2\)O. How many moles of tetraoxosulphate(vi)acid is needed to produce 0.5mol of aluminium tetraoxosulphate(vi)?

A.

0.5

B.

1.0

C.

1.5

D.

3.0

Correct answer is C

Where 3mols of H2So4 = 1 mol of (Al2SO4)3
y mols of H2SO4 = 0.5 mol of (Al2SO4)3
Then cross multiply to have:
y = \(\frac{3×0.5}{1}\)
y = 1.5 moles

382.

The most suitable indicator for the reaction between NaOH and HCOOH is?

A.

bromocresol

B.

methyl orange

C.

methyl red

D.

phenolphthalein

Correct answer is D

Phenolphthalein is suitable as indicator for this reaction i.e strong base and weak acid

383.

A sample of air was bubbled into water. The PH of the water slowly changed from 7 to 6. Which of the following gases in the samples caused the change?

A.

carbon(iv)oxide

B.

carbon(ii)oxide

C.

nitrogen

D.

oxygen

Correct answer is A

An acid gas is any gaseous compound which, when dissolved in water, will form an acidic solution

The most common acid gases are hydrogen sulfide (H2S) and carbon dioxide (CO2) gases

384.

Which of the following solutions containing one mole per dm\(^3\) of the compound would have the lowest PH?

A.

ethanoic acid

B.

hydrochloric acid

C.

sodium chloride

D.

sodium hydrogentrioxocarbonate(iv)

Correct answer is B

Low PH means strongly acidic cause acidity increases with decreasing PH values.

Example is Hydrochloric Acid

385.

Vinegar is an aqueous solution of?

A.

Hydrochloric acid

B.

ethanedioc acid

C.

ethanoic acid

D.

hydrofluoric acid

Correct answer is C

Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings