Thermodynamic energy problems (tutorial J ) are presented in a variety of ways designed to illustrate: the definitions of thermal energy changes, the transfer of thermal energy, how the energy of a reaction is measured and how the energy of a reaction can be calculated using thermodynamic data. The problems given here are meant to be only a representative sample.
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A mixture of propane and oxygen are burned in a cylinder equipped with a piston. The system loses 1200 J of heat to its surroundings and does 500 J of work in moving the piston. What is the change of the internal energy of the system? J·
The specific heat capacity of water is 4.184 J/gK. If you take 1 liter of water from a refrigerator at 4oC and let it warm to room temperature (24oC), how much heat is transferred to the water from its surroundings? J·
If a 100 g block of aluminum at 100oC is dropped into 1000 mL of water at 20oC, what would be the final temperature of the water? The specific heat capacity of aluminum is 0.908 J/gK. J·
Calculate the amount of heat in joules needed to change 50.0 g of ice at -30oC to superheated steam at 120oC. The specific heat of ice is 2.1 J/gK and the specific heat of steam is 2.0 J/gK. The heat of fusion for water is 333 J/g and the heat of vaporization for water is 2260 J/g. J·
What is the DHorxn for the burning of ethanol with oxygen? The balanced chemical equation is…C2H5OH (liq) + 3 O2 (gas)
® 2 CO2 (gas) + 3 H2O (liq)You will need to refer to tables of standard enthalpies of formation in order to solve this problem.
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Hydrazine is used as a rocket fuel. When hydrazine reacts with oxygen, the following reaction occurs…N2H4 (liq) + O2 (gas)
® N2 (gas) + H2O (gas)When 1.00 g of hydrazine is burned in a constant volume calorimeter, the change in temperature is +3.51 K. If the heat capacity of the bomb calorimeter is 5,510 J/gK,
what is the quantity of heat evolved in this reaction? What is the qrxn? J·
What is the DHorxn for the following reaction?H2C=CH2 + H2
® CH3–CH3You will need to refer to tables of bond energies in order to solve this problem.
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