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JAMB Chemistry 2014 Paper

Question : 13

Total: 45

[Pb = 207, N = 14, O = 16]

Solution:

Concept:

Solubility is the number of moles of solute dissolved in

1\ \text{dm}^3

of solution.

Explanation:

The solute is lead(II) trioxonitrate(V),

\mathrm{Pb(NO_3)_2}

Calculate its molar mass:

M = 207 + 2[14 + 3(16)] = 207 + 2(62) = 331\ \text{g mol}^{-1}

Moles of solute:

n = \frac{16.55}{331} = 0.05\ \text{mol}

Since

100\ \text{g}

of water has a volume of

0.1\ \text{dm}^3

20^\circ C

solubility

= \frac{\text{moles}}{\text{volume}} = \frac{0.05}{0.1} = 0.50\ \text{mol dm}^{-3}

Answer:

0.50\ \text{mol dm}^{-3}

This matches option D.

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