Question

A solution of an unknown compound has a concentration of 36.2% by mass. How many moles are present in 3.644 kg of solution if the solute has a molar mass pf 89.6 g/mol?

Answer 1

First part)

36.2% by mass means:

36.2 g of solute ------- 100 g of solution

Second part)

We want to know how many moles are present in 3.644 kg of solutions.

3.644 kg = 3644 g of solution

Now,

36.2 g of solute -------- 100 g of solution

x --------- 3644 g of solution

x = 1319 g of solute = 1320 g (3 significant figures)

Therefore 1320 g are diluted in 3644 g

Third part)

Number of moles = mass /molar mass

Number of moles = 1320 g of solute/ 89.6 g/mol of solute= 14.7 moles

Answer: 14.7 moles of solute