In: Chemistry
An aqueous solution contains 4.9 % NaCl by mass. You may want to reference ( pages 586 - 592) Section 13.5 while completing this problem. 1.Calculate the molality of the solution. Express the molality to two significant figures. Part B Calculate the mole fraction of the solution. Express the mole fraction to two significant figures.
part A
4.9 % NaCl by mass , 4.9 g of NaCl present in 100 g solution.
no of mole of NaCl present in soltion(n) = w/mwt = 4.9/58.5 = 0.084 mol
mass of solvent (w) = 100-4.9 = 95.1 g
molality(m) = n*1000/W
= 0.084*1000/95.1
= 0.88 m
part B
no of mole of NaCl present in soltion(n) = w/mwt = 4.9/58.5 = 0.084 mol
no of mole of water in solution = 95.1/18 = 5.283 mol
molefraction of NaCl = nNaCl/nTotal
= 0.084/(0.084+5.283) = 0.016
molefraction of water = nwater/nTotal
= 5.283/(0.084+5.283) = 0.984