Heat Capacity Problem?

Question

50g of H2O at 80 degree C are added to 150g of H2O at 25 degree C. If the temperature are allowed to equilibrate with no heat loss to the environment, what is the final temperature of the H2O?

Answer 1

As it's all water, the Specific Heat of water isn't required.

Total mass of water = 200g.

50g / 200g = 25% at 80°C. = 0.25 x 80 = 20.

150g / 200g = 75% at 25°C. = 0.75 x 25 = 18.75.

Final temp = 20°C + 18.75°C = 38.75°C (say 39°C).