Question

What is the mass of $0.20$ mole of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$ (ethanol)?

Answer 1

Given:

Moles of Ethanol ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$$=0.20\mathrm{mol}$

Step 1. Formula for mole

$\text{Mole}=\frac{\text{Mass of substance}\left(\text{g}\right)}{\text{Molar mass}}$

Step 2. Calculation of molar mass of Ethanol $\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)$

The molar mass of Ethanol$=(2\times \text{Atomic mass of}\text{C)}+(6\times \text{Atomic mass of hydrogen)+(1×Atomic mass of oxygen)}$

$=\left[\left(\text{2×12)+(6×1.0078)+(1×16}\right)\right]{\text{g mol}}^{-1}$$=46.0468{\text{g mol}}^{-1}$

Step 3. Calculation of mass:

$$\begin{gathered} 0.20\text{mol}=\frac{\text{Mass of ethanol}}{{\text{46.0468 g mol}}^{-1}} \\ \text{Mass of ethanol=}0.20\text{mol×}46.0468\text{g}{\mathrm{mol}}^{-1} \\ =9.209\text{g}\simeq 9.21\text{g} \end{gathered}$$

Hence, the mass of $0.20$ mole of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$ is $\mathbf{9}\mathbf{.}\mathbf{21}\mathbf{}\mathbf{\text{g}}$.