Question

How many moles of urea (60. g/mol) must be dissolved in 66.6g of water to give a 2.4 m solution?
a. 1.4 × 102 mol
b. 2.4 mol
c. 0.0024 mol
d. 0.15 mol
e. 9.0 × 102 mol

Answer 1

Answer:

d. 0.15 mol

Explanation:

Step 1: Given data

• Mass of water (solvent): 66.6 g

• Molality (m): 2.4 m

• Moles of urea (solute): ?

Step 2: Convert the mass of the solvent to kilograms

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

66.6 g × (1 kg/1,000 g) = 0.0666 kg

Step 3: Calculate the moles of solute

The molality is equal to the moles of solute divided by the kilograms of solvent.

m = moles of solute / kilograms of solvent

moles of solute = m × kilograms of solvent

moles of solute = 2.4 mol/kg × 0.0666 kg

moles of solute = 0.15 mol