Question

Two liquids A and B are at 20°C and 15°C. Their masses are in 2 - 3 and specific heats in ratio 3 : 4 then resultant temperature when they are mixed is
(A) 16.66°C
(B) 18.33°C
(C) 20°C
(D) 10°C​

Answer 1

Given:

Temperature of liquid A = 20°C

Temperature of liquid B = 15°C

Ratio of their masses = 2:3

Ratio of their specific heats = 3:4

To find:

The resultant temperature when the two liquids are mixed.

Solution:

The resultant temperature will be somewhere in between of both the temperatures and heat given out by liquid A = heat absorbed by liquid B

So m1 C1 ΔT1 = m2 C2 ΔT2

2m* 2C * (20-T) = 3m* 4C* (T-15)

4 * (20-T) = 12* (T-15)

80 - 4T = 12T - 180

12T+4T = 80+180

16T = 260

T = 16.25

Therefore the resultant temperature is 16.25°C.