Question

A compound with molar mass 146 gmol⁻¹ is used in nylon synthesis. If there are four oxygen atom per molecule of the compound, calculate the percentage (by mass) of oxygen in the compound:

• A. 43.83%
• B. 53.28%
• C. 49.28%
• D. 69.23%

Answer 1

Answer: (A)

43.83%

Answer 2

The percentage composition of an element in a compound is calculated as: $\text{Percentage by mass} = \frac{\text{Total mass of the element in one mole of the compound}}{\text{Molar mass of the compound}} \times 100\%$ Given: Molar mass of the compound = 146 g/mol Number of oxygen atoms per molecule = 4

The atomic mass of oxygen is approximately 15.999 g/mol.

1. Calculate the total mass of oxygen in one mole of the compound: Mass of oxygen = (Number of oxygen atoms) $\times$ (Atomic mass of oxygen) Mass of oxygen = $4 \times 15.999 \text{ g/mol} = 63.996 \text{ g/mol}$

2. Calculate the percentage of oxygen by mass: Percentage of oxygen = $\frac{63.996 \text{ g/mol}}{146 \text{ g/mol}} \times 100\%$ Percentage of oxygen $\approx 0.4383287... \times 100\%$ Percentage of oxygen $\approx 43.83287... \%$

Rounding to two decimal places, we get 43.83%.