Question

75.0 grams of MgCl₂ is dissolved in 500.0 g of water, density 1.00 g/mL. What is the MOLALITY of this solution?A) 0.50 mB) 1.00 mC) 1.58 mD) 2.02 m

Answer 1

C. Molality = 1.58 m

Step-by-step explanation

Given:

mass of MgCl2 = 75.0 g

mass of water = 500.0 g = 0.5 kg

density of water = 1.00 g/mL

Required: Molality of the solution

Solution

Step 1: Calculate the number of moles of MgCl2

n = m/M

n = 75.0g/95,211 g/mol

n = 0.788 mol

Step 2: calculate the molality

`\begin{gathered} Molality\text{ = }\frac{number\text{ of moles of solute \lparen mol\rparen}}{mass\text{ of solvent \lparen kg\rparen}} \\ Molality\text{ = }\frac{0.788\text{ mol}}{0.5\text{ kg}} \\ \\ Molality\text{ = 1.58 m} \end{gathered}`