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(B) Let the total weight of the solution be $100 \ g$. Since the solution is $28\%$ by weight of liquid $A$,the mass of $A$ is $28 \ g$ and the mass o

Vedclass · Accepted Answer

$0.04$

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(B) Let the total weight of the solution be $100 \ g$. Since the solution is $28\%$ by weight of liquid $A$,the mass of $A$ is $28 \ g$ and the mass of water $(H_2O)$ is $100 - 28 = 72 \ g$. The molar mass of $A$ $(m_w)$ is $140 \ g/mol$. The molar mass of water $(H_2O)$ is $18 \ g/mol$. Number of moles of $A$ $(n_A)$ = $\frac{28}{140} = 0.2 \ mol$. Number of moles of water $(n_w)$ = $\frac{72}{18} = 4.0 \ mol$. Mole fraction of $A$ $(x_A)$ = $\frac{n_A}{n_A + n_w} = \frac{0.2}{0.2 + 4.0} = \frac{0.2}{4.2} = \frac{1}{21} \approx 0.0476$. Rounding to the nearest provided option,the value is $0.04$.

An aqueous solution contains $28\%$ by weight of a liquid $A$ $(m_w = 140)$. The mole fraction of liquid $A$ is:

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