Review of Problem Types Internal Energy

HONORS CHEM I Chapter 6 Test Review of Problem Types 1. Internal Energy (∆E) given q and w • During the combustion of gasoline inside of an engine, a piston is forced to move, which requires 455 J of work from the burning fuel. Also, 1775 J of heat are produced by the burning fuel. If the system is defined to be the fuel, calculate the change in internal energy for the fuel. -2230 J • Suppose that the internal energy of a system increases by 1850 J when a mixture of hydrogen and oxygen gases burn. If the surroundings gain 875 J of heat, how much work was done by the system on the surroundings? 2725 J 2. Heat and Specific Heat Capacity • How much heat must be added to change the temperature of 255 g of H 2O from 25.0˚C to 55.0˚C. Cs for water is 4.18 J/g˚C. 3.20 x 104 J • 12.8 g of an unknown metal requires 88.5 J of heat to change its temperature from 10.5˚C to 20.0˚C. Find the specific heat capacity of the metal. 0.73 J/g°C • A 6.75 g piece of copper (Cs = 0.390 J/g˚C) gains 125 J of heat from its surroundings. If the piece of copper was initially at 34.0˚C, what is the final temperature of the copper? 81.5°C • A student wishes to determine the specific heat capacity of a metal by completing the following experiment. The student places a 5.45 g piece of metal, originally at 92.0°C, in a cup containing 28.5 g of water originally at 24.0°C. The water and the metal reach thermal equilibrium at 26.0°C. Find the heat gained by the water as well as the specific heat capacity of the metal. Cs for water is 4.18 J/g°C. 0.68 J/g°C 3. Pressure-Volume Work • A gas inside of a cylinder fitted with a piston expands from 5.75 L to 10.0 L against an external pressure of 2.1 atm. Find the amount of work performed by the gas. - 9.0 x 102 J • A gas performs 125.5 J of work by expanding against an external pressure of 1.3 atm. Find the change in volume of the gas. 0.95 L • A gas inside of a cylinder increases in volume by 9.8 L against an external pressure of 2.1 atm. If the gas also absorbs 124.0 J of heat form its surroundings during this process, what is ∆E? - 1976 J 4. Calorimetry • A 0.500 g sample of TNT (C7H5N2O6) is burned in a bomb calorimeter. During this process, the temperature changes from 20.00˚C to 68.00˚C. The heat capacity of the calorimeter is 420 J/ºC. Using this data, find ∆E for the combustion in kJ/mol TNT. – 8500 kJ/mol HONORS CHEM I 5. ∆Hrxn (with balanced equation) • Ethanol (C2H5OH) undergoes combustion according to the equation shown below. C2H 5OH (l) + 3 O2 (g) → 2 CO 2 (g) + 3 H 2O (l) ∆H = - 9500 kJ a.) How much heat (in kJ) is produced when 11.5 g of ethanol combusts? - 2400 kJ b.) How many grams of oxygen are required to produce 8800 kJ of heat? 89 g O2 6. ∆Hrxn (Hess’s Law) • Use the thermochemical equations shown below to find ∆H for the following reaction: CO2(g) C(s) + O2(g) 1189.2 kJ 2 H2O(l)  2 H2(g) + O2(g) ∆H = + 500.1 kJ CO2(g) + 2H2O(l) CH4(g) + 2O2(g) ∆H = + 1558.4 kJ CH4(g) C(s) + 2H2(g) ∆H = + 130.9 kJ • Use the thermochemical equations shown below to find ∆H for the following reaction: H2 O(g)  H2O(l) - 77 kJ H2S(g) + 2O2(g) H 2SO4(l) ∆ H = -549.5 kJ SO3(g) + H2O(g) H2SO4(l) ∆H = -143.5 kJ SO3(g) + H2O(l)  H2S(g) + 2O2(g) ∆H = +483 kJ 7. ∆H˚rxn (using ∆H˚f) • Calculate ∆H˚rxn for the following reaction using ∆H˚f values from the back of your textbook. NH 4Cl (s)  NH3 (g) + HCl 101.3 kJ/ mol • Calculate ∆H˚rxn for the following reaction using ∆H˚f values from the back of your textbook. N2O4 (g) + 4 H2 (g)  mol N 2 (g) + 4 H2O (g) - 978.3 kJ/