# Answer to Question #1478 in Molecular Physics | Thermodynamics for Rooky

Question #1478

If 200g of water at 20 degrees Celsius is combined with 100g of water at 80 degrees Celsius, what is the final temperature of the 200g of water?

Expert's answer

The final temperature of the 200g of water would be equal to the final temperature of the whole (200+100) mixture:

According to the heat balance equation,

Cm

Δ T

Δ T

200*(T-20) = 100* (80 - T)

2T-40 = 80 - T

3T = 120

T = 40 C.

According to the heat balance equation,

Cm

_{1}Δ T_{1}= Cm_{2}Δ T_{2}Δ T

_{1}= (T-20)Δ T

_{2}= (80-T)200*(T-20) = 100* (80 - T)

2T-40 = 80 - T

3T = 120

T = 40 C.

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