How many grams of KCl would you need to make 250 ml of a 0.5-M Solution w work?

Answer 1

Molar mass of KCl = 39 g/mol (K) + 35.5 g/mol (Cl) = 74.5 g/mol.

A 0.5 M solution is required (0.5 mol/L or 0.5 moles per litre).

0.5 moles of KCl is 0.5 mol x 74.5 g/mol = 37.25 g.

Dissolving this 37.25 g of KCl in a litre of water would give a 0.5 M solution.

If 1 L or 1000 mL of 0.5 M solution contains 0.5 moles then 1 mL of the same concentration solution would contain 0.5/1000 moles and 250 mL would contain 250 x 0.5/1000 moles = 0.125 moles.

0.125 moles of KCl is 0.125 mol x 74.5 g/mol = 9.31 g.