Hot water is supplied at 50 degrees c, cold water at 10 degrees c.
Calculate the mass of cold water that must be added to 100 kg of hot water to have 45 degrees c water

Use the principle of conservation of energy first. The energy lost by the hot water equals the energy gained by the cold water.

-Q_1 = Q_2

Change in energy of hot water is given by Q_1 = m_1c\theta_1

Change in energy of cold water is given by Q_2 = m_2c\theta_2

The hot water changes from 50 to 45 degrees. So, you get:

Q_1 = m_1c(45-50) = m_1c(-5)

5m_1c = m_2c\theta_2

c, the specific heat capacity is the same everywhere, so, it cancels out, and the initial mass of hot water is 100 kg. The cold water gets a rise in temperature from 10 to 45 degrees

5(100) = m_2(45-10)

You can find m_2, the mass of cold water required :)

Post what you get! :)

14.3kg,

Cheers

14.3kg, cheers

Right :)