Question

What mass (in g) of potassium bromide (KBr) is needed to make 0.250 L of a 0.320 M solution?

Answer 1

9.52 g of potassium bromide (KBr) is needed to make 0.250 L of a 0.320 M solution

Molarity is the number of moles of solute added per volume of the solution. It can be written as:

M = mol of solute/Litre of solution

    = (given weight/molecular weight) / (Volume in litre)

Putting the given values

0.320 M = (required weight/ 119 gmol^-1) / 0.250 L

0.320 mol L^-1 x 0.250 L = required weight/ 119 gmol^-1

0.08 mol x 119 gmol^-1 = required weight = 9.52 g