Question

What mass of water is required to dissolve 175 g KNO3 (potassium Nitrate) to produce a 32.25 m solution?

Answer 1

The mass of water is 0.0536 kg

STEP-BY-STEP EXPLANATION;

Given information

The mass of KNO3 = 175g

The molarity of the solution = 32.25 M

The molality formula is given below as

`\text{ Molality = mole of solute }/\text{ kg of solvent}`

The first step is to find the mole of the solute using the below formula

`\text{ Mole = mass }/\text{ molar mass}`

Recall, the molar mass of KNO3 is 101.1032 g/mol

`\begin{gathered} \text{ Mole = 175 }/\text{ 101.1032} \\ \text{ Mole = 1.731 moles} \end{gathered}`

The second step is to find the mass of water using the molality formula

`\begin{gathered} \text{ Molality = mole of solute }/\text{ kg of solvent} \\ 32.25\text{ = 1.731}/\text{ kg of solvent} \\ \text{ cross multiply} \\ \text{ 1.731 = 32.25 }*\text{ Kg of solvent} \\ \text{ kg of solvent = 1.731 }/\text{ 32.25} \\ \text{ kg of solvent = 0.0536 kg} \end{gathered}`

Hence, the mass of water is 0.0536 kg