Question

Calculate the molality of a 15.0% by mass solution of MgCl 2 in H 2O. The density of this solution is 1.127 g/mL. Group of answer choices

Answer 1

Answer:

1.86 m

Explanation:

Step 1: Calculate the mass of solute and solvent in 100 grams of solution

We have a 15.0% by mass solution of MgCl₂ (solute) in H₂O (water). In 100 g of solution, there are 15.0 g of solute and 100.0 g - 15.0 g = 85.0 g of solvent.

Step 2: Calculate the moles corresponding to 15.0 g of MgCl₂

The molar mass of MgCl₂ is 95.21 g/mol.

$15.0g \times \frac{1mol}{95.21 g} = 0.158mol$

Step 3: Convert the mass of water to kilograms

We will use the relationship 1 kg = 1,000 g.

$85.0g \times \frac{1kg}{1,000g} = 0.0850kg$

Step 4: Calculate the molality of the solution

$m = \frac{0.158mol}{0.0850kg} = 1.86m$

Answer 2

The molality is 1.86 m.

Given:

Mass solution of MgCl₂ in H₂O= 15%

Density= 1.127g/mL

To find:

Molality=?

Let's solve this question step by step:

Step 1: Calculate the mass of solute and solvent in 100 grams of solution

As it is given that 15.0% by mass solution of MgCl₂ (solute) in H₂O (water).

In 100 g of solution, there are 15.0 g of solute and 100.0 g - 15.0 g = 85.0 g of solvent.

Step 2: Calculate the moles corresponding to 15.0 g of MgCl₂

The molar mass of MgCl₂ is 95.21 g/mol.

Number of moles is given mass divided by the molar mass.

$\text{Number of moles}= \frac{15g}{95.21g/mol} =0.158mol$

Step 3: Convert the mass of water to kilograms.

As we know, 1 kg = 1,000 g.

$=\frac{85}{1000} =0.085kg$

Step 4: Calculate the molality of the solution.

Molality is a measure of the number of moles of solute in a solution corresponding to 1 kg or 1000 g of solvent.

$\text{Molality}=\frac{0.158\text{mol}}{0.085\tetx{kg}} =1.86 m$

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