Question

A solution is prepared by dissolving 25.0 g of ammonium sulfate in enough water to make 100.0 ml of stock solution. A 10.00 ml sample of this

stock solution is added to 50.00 ml of water. Calculate the concentration (in molarity) of ammonium ions and sulfate ions in the final solution

Answer 1

25 g (NH4)2SO4 in 100 mL soln.

Dilute 10 mL to 50 mL.

Concn is not 25 g x (10/50) = 5.0 g in the 50

moles (NH4)2SO4 = grams/molar mass

M = moles/L. (note: L is 0.050 from the 50 mL)

(SO4^-2) = [(NH4)2SO4]

(NH4^+) = 2 x [(NH4)2SO4]