Question

A solution is made by dissolving 24 g of NaCl to make 475 ml of solution. Calculate the concentration in units of molarity by following these steps: a) Convert the grams of NaCl to moles of NaCl. b) Calculate the liters of solution by dividing the given milliliters by 1000. c) Divide moles by the liters of solution.

Answer 1

1) Number of moles = (weight of solute in grams)/ (gram molecular weight)

For NaCl, gram molecular weight = 58.5

∴ Number of moles of NaCl = 24 / 58.5 = 0.408

2) 1 ml = 10^-3 liters
∴ 475 ml = 475 X 10^-3 liters = 0.475 liter

3) Molarity of solution =
`\frac{\text{number of moles of NaCl}}{\text{volume of solution in liters}}` =
`\frac{\text{0.408}}{\text{0.475}}` = 0.8589 M