Question

solution was prepared by dissolving 43.0 g of KCl in 225 g of water. Part A Calculate the mole fraction of the ionic species KCl in the solution. Express the concentration numerically as a mole fraction in decimal form. View Available Hint(s)

Answer 1

Answer: The mole fraction of KCl in the solution is 0.044

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$      .....(1)

• For KCl:

Given mass of KCl = 43.0 g

Molar mass of KCl = 74.5 g/mol

Putting values in equation 1, we get:

$\text{Moles of KCl}=\frac{43g}{74.5g/mol}=0.58mol$

• For water:

Given mass of water = 225 g

Molar mass of water = 18 g/mol

Putting values in equation 1, we get:

$\text{Moles of water}=\frac{225g}{18g/mol}=12.5mol$

To calculate the mole fraction of a substance, we use the equation:

$\chi_A=\frac{n_A}{n_A+n_B}$

Moles of KCl = 0.58 moles

Moles of water = 12.5 moles

Putting values in above equation:

$\chi_{KCl}=\frac{n_{KCl}}{n_{KCl}+n_{\text{water}}}$

$\chi_{KCl}=\frac{0.58}{0.58+12.5}\\\\\chi_{KCl}=0.044$

Hence, the mole fraction of KCl in the solution is 0.044