General Chemistry II
Thermochemistry
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Date: _____________ (Wag mo ako lokohin! Wala ka nun. HAHAHAHAH)
Problem Set #1
1. A piece of an unknown metal weighs 550. g and requires 9.315 kJ of energy to increase its temperature from 22.0 °C to 65.2 °C. What is the specific heat capacity of the metal?
2. What is the final temperature of a 275 kg sample of water, initially at 19.5 °C, if 36.5 kJ of heat were added to it? The specific heat capacity of water is 4.18 J/g°C.
3. A 45.0 g piece of aluminum, which is initially at 19.5 °C, is placed in 180.0 g of water, which is initially at 95.1 °C. What is the final temperature of the mixture once the aluminum and water reach thermal equilibrium? The specific heat capacity of water is 4.18 J/g°C and that of aluminum is 0.24 J/g°C.
4. If a reaction produces 1.506 kJ of heat, which is contained in 30.0 g of water that is initially at 26.5 °C, what is the resulting temperature of the water? The specific heat capacity of the water is 4.18 J/g°C.
5. When 1.025 g of naphthalene, C10H8, burns in a bomb calorimeter, the temperature rises from 24.25 °C to 32.33 °C. Find the enthalpy of combustion of naphthalene. The heat capacity of the calorimeter was determined to be 5.11 kJ/°C.
6. Zinc metal reacts with hydrochloric acid according to the balanced equation: Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g) When 0.110 g of Zn(s) is combined with 50.0 mL HCl solution in a coffee cup calorimeter, the temperature of the solution increased from 22.5 °C to 23.8 °C. Assuming an excess of HCl(aq), find the enthalpy of the reaction. The density of the solution is 1.03 g/mL and its specific heat capacity is 4.18 J/g°C.
7. When 0.740 g of trinitrotoluene (TNT), C7H5N2O6, is burned in a bomb calorimeter, the temperature increases from 23.4 °C to 26.9 °C. The heat capacity of the calorimeter is 534 J/°C, and it contains 675 g of water. What is the enthalpy of combustion of TNT?
8. When 50.0 g of 0.200 M NaCl(aq) is added to 100.0 g of 0.200 M AgNO3(aq), both initially at 24.1 °C, in a calorimeter, the temperature increases to 25.2 °C as AgCl(s) forms according to the chemical equation below. If the specific heat of the solution and products is 4.10 J/g°C, calculate the enthalpy of the reaction (∆Hrxn). (The density of the solution is 1.00 g/mL.) NaCl(aq) + AgNO3(aq) → AgCl(s) + NaNO3(aq)
9. The addition of 3.15 g of Ba(OH)2⋅8H2O to a solution of 1.52 g of NH4SCN in 1.00 kg of water in a calorimeter caused the temperature of the solution to fall by 30.1 °C. Assume the mass of the reactants and products is negligible compared to the mass of the water and that the specific heat of the solution is 4.20 J/g°C. Calculate the enthalpy of the reaction in kJ/mol: Ba(OH)2⋅8H2O(s) + 2 NH4SCN(aq) → Ba(SCN)2(aq) + 2 NH3(aq) + 10 H2O(l)
