Question

How much potassium bromide (KBr), in grams, should be added to water to prepare a .50 L of solution with a molarity of .125 M?

Answer 1

Given conditions,

Molarity of the Solution = 0.125 M.

Volume of the solution = 0.50 L.

Using the formula of the Molarity,

Molarity = no. of moles of solute/Volume of solution in L.

Now,

No. of the moles of the solute = Molarity × Volume of the solution in L.

∴ No. of moles of the solute = 0.125 × 0.5

∴ No. of moles = 0.0625 moles.

No. of moles of solute means that the no. of moles of KBr.

No. of moles of KBr. = Mass/Molar mass.

∴ Mass of the KBr = No. of moles of KBr × Molar Mass.

∴ Mass of the KBr = 0.0625 × 119

∴ Mass of the KBr = 7.4375 g.

Hope it helps.