Chapter 14, Problem 118A

Interpretation Introduction

Interpretation: To calculate the percent composition of 2-propanol.

Concept Introduction: A chemical compound is made up of different types of atoms. Percent composition defines the percent of each atom in the given compound. The percent composition can be calculated by using the formula

  $\text{Percentcomposition=}\frac{\text{massofelement}}{\text{molecularweightofthecompound}}\times 100$

Answer to Problem 118A

Explanation of Solution

The chemical formula of 2-propanol is given ${\text{C}}_{\text{3}}{\text{H}}_{\text{7}}\text{OH}$

First the formula mass of the compound has to be calculated.

Molar mass of each element in the compound should be calculated first.

There are three carbons in the compound and the molar mass of a single carbon atom is 12 g/mol therefore for three carbons it will be $\text{3}\times \text{12}\frac{\text{g}}{\text{mol}}=36\frac{\text{g}}{\text{mol}}$ .

There are eight hydrogen atoms in the given molecular formula. Molar mass of one hydrogen atom is 1 g/mol. Therefore, the molar mass of eight hydrogen atoms will be $8\times \text{1}\frac{\text{g}}{\text{mol}}=8\frac{\text{g}}{\text{mol}}$

There is only one oxygen atom in the given molecular formula. Molar mass of one oxygen atom is 16 g/mol. Therefore, the molar mass of oxygen atom will be $1\times \text{16}\frac{\text{g}}{\text{mol}}=16\frac{\text{g}}{\text{mol}}$

Therefore, the formula mass of the given compound is $36+8+16=60$

The percent composition of carbon in the given compound will be:

  $\text{Percentcomposition=}\frac{36}{60}\times 100=60\%$

The precent composition of hydrogen in the given compound will be:

  $\text{Percentcomposition=}\frac{8}{60}\times 100=13.4\%$

The percent composition of oxygen in the given compound will be:

  $\text{Percentcomposition=}\frac{16}{60}\times 100=26.6\%$

Conclusion

The precent composition of each element in the compound expresses the composition of each element in the given compound. The quantity of the element is expressed in terms of grams of element present.