A quantity of hot water at 100ºC is added to 400g of water at 10ºC until the temperature of the mixture is 60ºC. Calculate the mass of the hot water added. [Specific heat capacity of water =4200JKg-1 K-1]

A. 200g
B. 320g
C. 400g
D. 500g

Correct Answer: Option D

D. 500g

Explanation

Heat lost by hot water = Heat gained by cold water

M x 4200 x (100 – 60 = 0.4 x 4200 x (60 – 10)

4200m x 40 = 0.4 x 4200 x 50

40m = 0.4 x 50

m = 0.4×50/40 = 0.5kg

= 500g