What is the molality of 67.1g of Nano3 in 2.5l of water
i get the molar mass of nano3 and divide it by the 67.1g and multipy it by 2.5l
Nope. You have it backwards (actually you want the reciprocal of what you wrote).
Its grams/molar mass = mols
Then mols/2.5 = m