Some very hot rocks have a temperature of 720 ^o C and a specific heat of 250 J/(Kg*K). The rocks are bathed in 50 L of boiling water. If the heat of the rocks completely vaporizes the water, what is the minimum combined mass of the rocks?

1 Answer
Jul 23, 2017

The mass of the rocks is =728.1kg

Explanation:

The heat transferred from the hot rocks to the water, is equal to the heat used to evaporate the water.

For the rocks DeltaT_o=720-100=620^@

Heat of vaporisation of water

H_w=2257kJkg^-1

The specific heat of the rocks is

C_o=0,25kJkg^-1K^-1

The mass of water is m_w=50kg

m_o C_o (DeltaT_o) = m_w H_w

m_o*0.25*620=50*2257

The mass of the rocks is

m_o=(50*2257)/(0,25*620)

=728.1kg