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 is D

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 = \(\frac{0.4 \times 50}{40}\) = 0.5kg

= 500g