Question

the density of 3 molar solution of NaCl is 1.25 gram ml calculate the molality of the solution

Answer 1

Use formula ,
1/m = d/M - Ms/1000
where ,
m is molatity of solution
d is density of solution
M is molarity of solution
Ms is molar mass of solute

here ,
M = 3 molar
d = 1.25 g/ml
Ms = 23 + 35.5 = 58.5 g/mol
m = ?

1/m = 1.25/3 - 58.5/1000
1/m = 5/12 - 0.0585
1/m = 0.358
m = 1/0.358 = 2.8
m = 2.8

hence, molatity = 2.8 molal