Chapter 10, Problem 192A

Interpretation Introduction

Interpretation:

Empirical formula of the molecule present in skunk spray must be found for which % of C, H and S are is 44.77, 7.46 and 47.76 respectively.

Concept introduction:

Empirical formula of a molecule is the smallest unit which is repeated in the molecule.

Answer to Problem 192A

The empirical formula is C₅H₁₀S₂.

Explanation of Solution

% of C, H and S are 44.77, 7.46 and 47.76 respectively.

Considering 100 g of compound, the mass of C, H and S is 44.77 g, 7.46 g and 47.76 g respectively.

Also, the molar mass of C, H and S is 12 g/mol, 1 g/mol and 32 g/mol respectively.

Therefore, number of moles of C, H and S can be calculated as follows:

Moles of C $\text{=}\frac{\text{44}\text{.77 g}}{\text{12 g/mol}}\text{=3}\text{.73 mol}$

Moles of H $=\frac{7.46\text{ g}}{1\text{ g/mol}}=7.46\text{ mol}$

Moles of S $=\frac{47.76\text{ g}}{32\text{ g/mol}}=1.49\text{ mol}$

Smallest mole ratio C: H: S can be obtained as follows:

$\begin{array}{l}=\frac{3.73}{1.49}:\frac{7.46}{1.49}:\frac{1.49}{1.49}\\ =2.5:5.0:1=5:10:2.\end{array}$

Thus empirical formula is C₅H₁₀S₂.

Conclusion

Empirical formula of the molecule is C₅H₁₀S₂.