the formula for molality---> m = moles solute/ Kg of solvent
the solute here is NH₃ because it's the one with less amount. which makes water the solvent.
1) let's convert the grams of NH₃ to moles using the molar mass
molar mass of NH₃= 14.0 + (3 x 1.01)= 17.03 g/ mol
30.0 g (1 mol/ 17.03 g)= 1.76 mol NH₃
2) let's convert the grams of water into kilograms (just divide by 1000)
70.0g= 0.0700 kg
3) let's plug in the values into the molality formula
molality= mol/ Kg---> 1.76 mol/ 0.070 kg= 25.1 m
