A saturated solution of potassium trioxochlorate(V), \text{KClO}_3, contains 7.35\text{ g}… — JAMB UTME

A saturated solution of potassium trioxochlorate(V), $\text{KClO}_3$ , contains $7.35\text{ g}$ of the salt dissolved in $250\text{ cm}^3$ of solution at $25^\circ\text{C}$ . What is the solubility of $\text{KClO}_3$ at $25^\circ\text{C}$ in $\text{mol dm}^{-3}$ ?
$[\text{K} = 39.0,\text{ Cl} = 35.5,\text{ O} = 16.0]$

$0.24\text{ mol dm}^{-3}$ Answer
B
$0.06\text{ mol dm}^{-3}$
C
$29.40\text{ mol dm}^{-3}$
D
$0.48\text{ mol dm}^{-3}$

Answer

The solubility of potassium trioxochlorate(V) at

25^\circ\text{C}

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

The correct answer is

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

because

7.35\text{ g}

\text{KClO}_3

corresponds to

0.06\text{ mol}

. Dissolving

0.06\text{ mol}

0.25\text{ dm}^3

gives a molar concentration of

\frac{0.06}{0.25} = 0.24\text{ mol dm}^{-3}

Step-by-Step Solution

Calculate the molar mass of

\text{KClO}_3

\text{Molar Mass} = 39.0 + 35.5 + (3 \times 16.0) = 122.5\text{ g mol}^{-1}

Molar mass is required to convert mass of solute to amount in moles.

Calculate the number of moles of

\text{KClO}_3

7.35\text{ g}

\text{Moles of } \text{KClO}_3 = \frac{7.35\text{ g}}{122.5\text{ g mol}^{-1}} = 0.060\text{ mol}

Solubility in

\text{mol dm}^{-3}

measures moles of solute per unit volume of solution.

Convert solution volume to

\text{dm}^3

and calculate molar solubility

\text{Volume} = \frac{250\text{ cm}^3}{1000} = 0.250\text{ dm}^3

;

\text{Solubility} = \frac{0.060\text{ mol}}{0.250\text{ dm}^3} = 0.24\text{ mol dm}^{-3}

Dividing total moles by total volume in cubic decimeters yields concentration in

\text{mol dm}^{-3}

Key Concept

Solubility concentration calculations in mol/dm³

Estimated Time:1m 30s

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