Question

What molality of a nonvolatile, nonelectrolyte solute is needed to raise the boiling point of water by 7.10°c (kb = 0.520°c/m)?

Answer 1

According to boiling point elevation equation:
Δ T = i Kb m
when ΔT (change in boiling point) = 7.10 C° 
and i (van't Hoff factor)= 1
and Kb = 0.520
so, by substitution:
7.10 = 1*0.520 *m
m = 7.1 / 0.52 = 13.65 m