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Concentration Terms - An Introduction (w/w etc)

A sample of c...

Question

A sample of chalk contains clay as impurity. The clay impurity loses $11 %$ of its weight as moisture on prolong heating. $5$ gram sample of chalk on heating shows a loss is weight (due to evolution of $C O_{2}$ and water) by $1.1 g$ . Calculate $%$ of chalk $(C a C O_{3})$ in the sample.

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Solution

Let the mass of chalk in 5g be x grams,
Therefore, mass of clay = (5 - x) grams.
Mass of moisture lost by clay = (5 - x) x $\frac{11}{100}$
= (0.55 - 0.11x) grams.
Now,
$C a C O_{3} H e a t - ----- \to C a O + C O_{2} ↑$
Molar mass of $C a C O_{3}$ is 100g, loss its mass by 44 g in the form of $C O_{2}$ gas
Therefore,
44 g of $C O_{2}$ is lost by 100 g chalk
So,
x gram $C O_{2}$ is lost by $\frac{44}{100}$ is multiplied by x = 0.44x grams
Total mass lost from 5 g of chalk/clay = 1.1g
Therefore,
(0.55 - 0.11x) + 0.44x grams = 1.1g
0.33x = 1.1 - 0.55
0.33x = 0.55
x = 1.67g
Hence, % of chalk in sample = $\frac{1, 67}{5}$ x 100
= 33.4 %
Chalk $(C a C O_{3})$ release $C O_{2}$ on heating.
33% $C O_{2}$ IS LOSS

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