Question

At 20°C, a 0.756 M aqueous solution of ammonium chloride has a density of 1.0107 g/mL. What is the mass % of ammonium chloride in the solution? The formula weight of NH4Cl is 53.50 g/mol.

Answer 1

Answer:

$\%m/m=4\%$

Explanation:

Hello,

In this case, by knowing that the molarity is measured in molal units which are mole per liter of solution and the by-mass percentage demands us to compute the mass of the solution, we proceed by assuming 1 L of solution:

$m_{solution}=1L*\frac{1000mL}{1L}*\frac{1.0107g}{1mL} =1010.7g$

Then, for 1 L of solution, we have 0.756 moles of solute (ammonium chloride), so we compute the grams for those moles by using its molar mass of 53.491 g/mol as shown below:

$m_{solute}=0.756mol*\frac{53.491g}{1mol}=40.4g$

Finally, we compute the by-mass percentage as shown below:

$\%m/m=\frac{m_{solute}}{m_{solution}} *100\%=\frac{40.4g}{1010.7g}*100 \%\\\\\%m/m=4\%$

Best regards.