THERMOCHEMISTRY WORKSHEET 6 Calorimetry.pdf

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Chemistry

Name: _____________________________ THERMOCHEMISTRY WORKSHEET #6

Calorimetry 1.

A student mixed 100.0 mL of 1.0 mol/L sulfuric acid with 100.0 mL of 1.0 mol/L potassium hydroxide in a simple calorimeter. Both solutions were initially at 19.67 oC and the highest temperature reached by the reaction mixture was 34.06oC. a) Find the heat change for this reaction. (Ans: -12.04 kJ)

b) Find the molar heat of neutralization for the acid. (-120.4 kJ/mol)

2.

A 2.24 g sample of ammonium nitrate is added to 78.44 mL of water in a simple calorimeter. The sample completely dissolves and causes the water temperature to change from 22.13 oC to 20.15oC. a)

Calculate the heat change associated with dissolving the ammonium nitrate. (Ans: 0.668 kJ)

b)

Is the process exothermic or endothermic? Explain.

c)

What assumptions are being made in your solution to the question?

d)

Find the molar heat of solution for ammonium nitrate. (Ans: 23.9 kJ/mol)

Chemistry 3.

Name: _____________________________

A very cold piece of silver with a mass of 75.84 g is added to a simple calorimeter that contains 150.0 mL of water. The temperature of the calorimeter water changes from 19.47 oC to 16.24oC. Note: Do not add the mass of silver to total mass since it does not dissolve in the water. a)

Find the heat change for the piece of silver. (Ans: 2.03 kJ)

b)

How cold was the piece of silver, originally (find Ti)? (cAg = 0.237 J/goC) (Ans: -97 oC)

4.

A 5.00 g sample of solid benzene (C6H6) is added to a simple calorimeter that contains 0.125 kg of ethanol. Given that the specific heat capacity of ethanol is 2.4 kJ/kg . oC, and that the temperature changed from 21.05oC to 19.39oC, what is the molar heat of fusion for the benzene? Note: Ethanol is the surroundings, not water and benzene dissolves in the ethanol. (Ans: 8.1 kJ/mol)

5.

A 5.00 g sample of acetylene undergoes complete combustion in an oxygen bomb calorimeter. The calorimeter has a heat capacity of 6.49 kJ/oC. The maximum temperature increase is recorded as 9.50oC. Find the molar heat of combustion for acetylene, C2H2. (Ans: -3.21  102 kJ/mol)