What is the molarity of 62grams of ammonium in 5liters of water?

First we need to find how many moles of ammonium weigh 62 grams.

Molar mass of NH4 = (14.0) + (4*1.0) grams

or 18.0 grams/mole

62 (g) / 18 (g/mole) = 3.444 ... moles of NH4

If it is dissolved in 5 litres of water, the concentration will be 3.444moles/5L

or 0.6888 M.