IMF worksheet - Phase Changes and Calculations PDF

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IMF assignments: IMF worksheet - Phase Changes and Calculations.
In the heating and cooling curves we learned that energy is absorbed by a substance as it melts or boils (vaporizes) and energy is released from a substance as it freezes or condenses....

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AP Chemistry IMF Worksheet: Phase Changes and Calculations NAME: __________________________________________________

In the heating and cooling curves we learned that energy is absorbed by a substance as it melts or boils (vaporizes) and energy is released from a substance as it freezes or condenses. The energies involved are the Heat of Vaporization (liquid  gas) and the Heat of Fusion (solid  liquid). These energies will be used as conversion factors: Heat of Vaporization or Heat of Fusion (melting) or Heat of Condensation Heat of Solidification of water of water Hvap =

2250 J gram

Hfus =

333 J gram

Do the following calculations. Show your equation for each problem. Box your answers. 1.

2.

Calculate the energy needed to vaporize… a)

15.0 g of water

b)

5.75 kg of water

c)

3.88 moles of water

Calculate the energy needed to melt… a)

23.0 g of water

b)

8.75 kg of water

c)

3.25 moles of water

Recall that, when calculating energy needed to bring a substance from one temperature to another temperature along its heating or cooling curve, that an energy calculation must be performed for every line segment of the curve. With this in mind, answer the following questions. (*Hint: Sketch a graph showing the processes that are occurring)

1. Ethanol, C 2H5OH, melts at -114°C and boils at 78°C. The enthalpy of fusion of ethanol is 5.02 kJ/mol, and its enthalpy of vaporization is 38.56 kJ/mol. The specific heats of solid and liquid ethanol are 0.97 J/g∙⁰C and 2.3 J/g∙⁰C, respectively. How much heat is required to convert 75.0 g of ethanol at -120°C to the vapor phase at 78°C?

2. Freon-11TM, which has the chemical formula CCl3F, has a normal boiling point of 23.8°C. The specific heats of CCl3F(l) and CCl3F(g) are 0.87 J/g∙⁰C and 0.59 J/g∙⁰C, respectively. The heat of vaporization for the compound is 24.75 kJ/mol. Calculate the heat required to convert 10.0 g of Freon-11 TM from a liquid at -50.0°C to a gas at 50.0°C....