Question

2. Sixty grams of water is at an initial temperature of 24 °C.

Calculate the heat required to completely convert the 100 ºC water to steam. (The latent heat of vaporization of water is 540 cal/g.)

The heat required to completely convert the 100 ºC water to steam is... kcal?

3. How much heat is required to raise the temperature of 140 g of water from 12°C to 88°C? The specific heat capacity of water is 1 cal/g·°C.

The heat required is  cal?

4. Calculate the amount of heat that must be removed from an 300-g block of aluminum to lower its temperature from 160°C to 40°C. The specific heat capacity of aluminum is 0.215 cal/g·°C.

The amount of heat that must be removed from the block of aluminum is  cal.

Answer 1

2.

Heat required is given by:

Q = Q1 + Q2 + Q3

Q1 = Heat required from 24 C water to 100 C water

Q2 = Heat required for phase change from liquid to steam

So,

Q = Mi*Cw*dT1 + Mi*Lv

dT1 = 100 - 24 = 76

Cw = Specific heat of water = 1 cal/gm-C

Mi = mass of ice = 60 gm

Lv = latent heat of vaporization = 540 cal/gm

Using above values:

Q = 60*1*76 + 60*540

Q = 36960 Cal = 36.96 kCal

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3.

Heat required = Q = m*Cw*dT

Q = 140*1*(88 - 12) = 10640 Cal

Q = energy required = 10640 cal

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