WAEC Chemistry Past Questions & Answers - Page 172

856.

14.8 g of a salt (z)dissolved in 250 cm3 of distilled water gives a concentration of 0.80 mol dm-3. Calculate the molar mass of the salt (z).

A.

13.5 g mol-1

B.

18.5 g mol-1

C.

47.4 g mol-1

D.

74.0 g mol-1

Correct answer is D

250cm3 of distilled water contains 14.8g of salt(z)
1cm3 of distilled water will contain \(\frac{14.8 x 1}{250}\) of salt (z)
:. 1000cm3 of distilled water will contain \(\frac{14.8 x 1 x 1000}{250}\) = 59.2g/dm33 = \(\frac{concentration in g/dm3}{molar mass}
0.80 = \(\frac{59.2}{molar mass}\)
molar mass = \(\frac{59.2}{0.80}\) = 74.0 g/mol

857.

Which of the following species does not contain a co-ordinate bond?

A.

AI2CI6

B.

CCI4

C.

H3O+

D.

NH + 4

Correct answer is A

No explanation has been provided for this answer.

858.

Which of the following compounds has hydrogen bonds between its molecules?

A.

HF

B.

HBr

C.

HCI

D.

HI

Correct answer is A

No explanation has been provided for this answer.

859.

If the difference between the electronegativities of two elements is large, the type of bond that can be formed between them is

A.

covalent

B.

dative

C.

ionic

D.

metallic

Correct answer is C

No explanation has been provided for this answer.

860.

Which of the following statements about sodium is not true?

A.

Na+ is smaller in size than Na

B.

Na is smaller in size than Na+

C.

Na+ has fewer electrons than Na

D.

The effective nuclear charge in Na+ is greater than in Na

Correct answer is B

No explanation has been provided for this answer.