During a study trip, students visited a lake and took out water sample which was rich in potassium…

During a study trip, students visited a lake and took out water sample which was rich in potassium chloride salt. They performed an experiment to calculate the boiling point of lake water which was found to be $100.025^\circ\text{C}$. If 500 g of the water sample was used for calculation ($K_b = 0.52\text{ K kg mol}^{-1}$) and there was 0.42 g KCl in the 500 ml sample, what is the observed molecular mass of KCl in the lake sample?