# Question #e2397

##### 1 Answer

The mass of urea is 26.1 g.

This is a freezing point depression problem.

In your problem, we have to work backwards from the freezing point to calculate the mass of solute.

**Step 1.** Calculate

**Step 2.** Calculate

Since urea is a nonelectrolyte,

**Step 3.** Calculate the molality

**Step 4.** Calculate the moles of urea

Moles of urea =

**Step 5.** Calculate the mass of urea

The formula of urea is NH₂CONH₂. The molar mass is 60.06 g·mol⁻¹.

Moles =

Mass = moles × molar mass = 0.435 mol × 60.06 g·mol⁻¹ = 26.1 g

The mass of urea is 26.1 g.