WAEC Chemistry Past Questions & Answers - Page 261

1,301.

What volume of distilled water should be added to 400cm3 of 2.0 mole dm-3 \(H_{2}SO_{4}\) to obtain 0.20 mole dm-3 of solution>

A.

600cm-3

B.

800cm-3

C.

1,000cm-3

D.

3,600cm-3

E.

4,000cm-3

Correct answer is D

\(400cm^{3} \to 2moldm^{-3}\)

\(0.4 dm^{3} \to 2moldm^{-3}\)

Multiplying in order to get the moles of the acid.

\(0.4dm^{3} \times 2moldm^{-3} = 0.8moles\)

After diluting to \(0.2moldm^{-3}\), the new volume will be

\(\frac{0.8}{0.2} = 4dm^{3}\)

Converting back to cm^3,

We have \(4 \times 1000cm^{3} = 4000cm^{3}\)

Hence, the volume of water added = \((4000 - 400)cm^{3} = 3600cm^{3}\)

1,302.

The following gases decolorize bromine water except

A.

C2H6

B.

C2H4

C.

C2H2

D.

C3H4

E.

C3H6

Correct answer is A

No explanation has been provided for this answer.

1,303.

Consider the reaction represented by the following equation CaCI2 (aq) + H 2C2O 4(aq) ⇌ CaC 2O4(s) + 2HCI(aq). Which of the following would dissolve the precipitate of CaC 2O4 formed?

A.

Stirring the mixture vigorously

B.

Adding more calcium chloride solution

C.

lncreasing the concentration of the ethanedioic acid

D.

Adding concentrated hydrochloric acid

E.

Adding some distilled water

Correct answer is D

No explanation has been provided for this answer.

1,304.

Some precious stones such as ruby and sapphire consist of aluminum oxide coloured by traces of the oxides of

A.

group lV elements

B.

group l metals

C.

transition metals

D.

alkaline earths

E.

the halogens

Correct answer is C

No explanation has been provided for this answer.

1,305.

Which of the following pieces of deposited if a current of 10A was passed through a solution of copper(ll) salt for 965 seconds? (1F = 96500 C)

A.

0.005 mole

B.

0.025 mole

C.

0.05 mole

D.

1.00 mole

E.

1.05 mole

Correct answer is C

No explanation has been provided for this answer.