# Question #10c19

##### 1 Answer

#### Answer:

You also need the percent composition of the solution. Here's how to do the calculation with a specific example.

#### Explanation:

**Example**

What is the molarity of an 87.0 % (m/m) solution of phosphoric acid that has a molality of 68.3 mol/kg and a density of 1.46 g/mL?

**Solution**

**Step 1:** Assume some convenient amount of phosphoric acid solution.

I choose to assume a mass of 1 kg of the solution. Then

**Step 2:** Calculate the mass of water

**Step 3:** Calculate the moles of

**Step 4:** Calculate the volume of the solution

**Step 5:** Calculate the molarity of the solution