Question

How to find molar mass

Answer 1

moles H3PO4 = 87.0 g / 97.9937 g/mol = 0.8878 mol 
kg of water = 0.0130 kg

molality = 0.8878 mol / 0.0130 kg = 68.3 molal

Answer 2

Molar Mass= Mass of given substance/amount of substance