WAEC Chemistry Past Questions & Answers - Page 212

1,056.

The gas evolved when dilute tetraoxosulphate (VI) acid reacts with sodium hydrogen trioxocarbonate (IV) is

A.

hydrogen

B.

oxygen

C.

carbon (IV) oxide

D.

sulphur (VI) oxide

Correct answer is C

No explanation has been provided for this answer.

1,057.

Which of the following gases is colourless, odourless and soluble in potassium hydroxide solution?

A.

NO 2

B.

SO 2

C.

NH 3

D.

CO2

Correct answer is D

CO2 (carbon dioxide) is a colorless and odourless gas and very soluble in KOH owning that it is an acidic gas.

1,058.

9.60 g of a gas X occupies the same volume at 0.30 g of hydrogen under the same conditions. Calculate the molar mass of X [H = 1]

A.

8g mol -1

B.

16 gmol -1

C.

32g mol -1

D.

64g mol -1

Correct answer is C

Using the ideal gas equation, 

PV = nRT.

where \(n = \frac{mass}{\text{molar mass}}\).

For Hydrogen, \(\frac{m_H}{M_H} = \frac{PV}{RT}\).

For element X, \(\frac{m_X}{M_X} = \frac{PV}{RT}\)

Under the same conditions implies \(\frac{PV}{RT}\) is the same for both hydrogen and X.

\(\frac{m_H}{M_H} = \frac{m_X}{M_X}\)

Molar mass of X = \(\frac{\text{molar mass of hydrogen} \times \text{mass of X}}{\text{mass of hydrogen}}\)

= \(\frac{1 \times 9.6}{0.3}\)

= 32 g/mol

1,059.

Which of the following increases as boiling water changes to steam?

A.

temperature of the system

B.

degree of disorder in the system

C.

number of molecules

D.

activation energy

Correct answer is B

No explanation has been provided for this answer.

1,060.

What is the shape of a molecule of CCI4?

A.

Pyramidal

B.

Tetrahedral

C.

Trigonal planar

D.

Linear

Correct answer is B

No explanation has been provided for this answer.