Question

Calculate the molarity and the molality of an NH3 solution made up of 30 g of NH3 in 70 g of water. The density of the solution is 0.982 g/ml.

Molar Mass of NH3 = 17.04 g

Answer 1

I think I got the answer. Can some please check it.

Molarity = 17.3 mol/L = 17.3 M

Molality = 25.1 mol/kg = 25.1 m

Answer 2

I confirmed 25.1 m but not 17.3 M.

moles NH3 = 30/17.04 = ??
volume = mass/density = 70/0.982 = xx and that divided by 1000 to convert to L = zz.
Then M = ??moles/zzL

Answer 3

20.1

Answer 4

20.1

Answer 5

The solution of 30% (w/w) NH3, i.e. 30 g NH3 + 70 g H2O = 100 g.
with d = 0.982 g/ml -> 100 g solution = 101.8 ml; and molality = 30 g (NH3)/17 (g/mol) = 1.76 mol of NH3 in 100 g (or 101.8 ml) solution; So Cm = 1.76 (mol)*1000 (ml)/101.8 (ml) = 17.3 mol/L

Answer 6

why are we multiplying by 1000