What is the solubility of a salt if 0.4g of it is obtained on evaporating 200{cm}³ of its saturated solution to dryness?

Correct Answer is : 2.00gdm−3{gdm}^{-3}gdm−3

Correct Answer is : 2.00gdm−3{gdm}^{-3}gdm−3

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WAEC Chemistry 2018 Paper

Question : 5

Total: 50

\mathrm{cm}^{3}

of its saturated solution to dryness?

Solution:

Concept:

Solubility is the maximum mass of solute dissolved in

1\,\mathrm{dm}^{3}

of a saturated solution.

Explanation:

Convert the volume to

\mathrm{dm}^{3}

Since

1000\,\mathrm{cm}^{3} = 1\,\mathrm{dm}^{3}

200\,\mathrm{cm}^{3} = \frac{200}{1000}\,\mathrm{dm}^{3} = 0.2\,\mathrm{dm}^{3}

This

0.2\,\mathrm{dm}^{3}

of solution contains

0.4\,\mathrm{g}

of salt.

Solubility is the mass dissolved in

1\,\mathrm{dm}^{3}

\text{Solubility} = \frac{0.4\,\mathrm{g}}{0.2\,\mathrm{dm}^{3}} = 2.0\,\mathrm{gdm}^{-3}

Answer:

2.00\,\mathrm{gdm}^{-3}

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