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Thermochemistry Worksheet #1
1. The reaction of magnesium with sulfuric acid was carried out in a calorimeter. This reaction caused the temperature of 27.0 grams of liquid water, within the calorimeter, to raise from 25.0C to 76.0C. Calculate the energy associated with this reaction. Answer: 5760J
2. The reaction of zinc with nitric acid was carried out in a calorimeter. This reaction caused the temperature of 72.0 grams of liquid water, within the calorimeter, to raise from 25.0C to 100.C. Calculate the energy associated with this reaction. Answer: 22,600J
3. A 4.00 gram sample of solid gold was heated from 274K to 314K. How much energy was involved?
Answer: 20.6J
Use Hf values (table found in notes) to solve the following problems.
4. Determine the H for each of the following reactions. Classify each reaction as either exothermic or endothermic.
a. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)H = ? kJ/mol
b. H2 (g) + Cl2(g) 2HCl(g) H = ? kJ/mol
c. CH4(g) + 2O2(g) CO2(g) + 2H2O(g)H = ? kJ/mol
d. 2F2(g) + 2H2O(l) 4HF(g) + O2(g)H = ? kJ/mol
e. Na2O(s) + SO2(g) Na2SO3(s)H = ? kJ/mol
5. Use Hf values to solve the following problems. The production of steel from iron involves the removal of many impurities in the iron ore. The following equations show some of the purifying reactions. Calculate the enthalpy (H) for each reaction.
a.3C(s) + Fe2O3(s) 3CO(g) + 2Fe(s)H = ? kJ/mol
b.3Mn(s) + Fe2O3(s) 3MnO(s) + 2Fe(s)H = ? kJ/mol
c.12P(s) + 10Fe2O3(s) 3P4O10(s) + 20Fe(s)H = ? kJ/mol
d.3Si(s) + 2Fe2O3(s) 3SiO2(s) + 4Fe(s)H = ? kJ/mol
e.3S(s) + 2Fe2O3(s) 3SO2(g) + 4Fe(s)H = ? kJ/mol
Answers:5a. 786.8kJ/mol, 2b. -36.3kJ/mol, 2c. 2154.3kJ/mol, 2d. -495.9kJ/mol, 2e. 1346.4kJ/mol
Thermochemistry Worksheet #2
Hess’s Law Problems
1. Calculate the heat of the reaction for the following reaction:
2F2(g) + 2H2O(l) 4HF(g) + O2(g)H = ? kJ/mol
Use heat of formation values. Is this reaction exothermic or endothermic? Answer: -521.6kJ/mol
2. Calculate the heat of the reaction for the following reaction:
Na2O(s) + SO2(g) Na2SO3(s)H = ? kJ/mol
Use heat of formation values. Is this reaction exothermic or endothermic? Answer: -390.0kJ/mol
3. Given the following two reactions and enthalpy data:
CH2CO(g) + 2O2(g) 2CO2(g) + H2O(g)H = 981.1 kJ
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)H = 802.3 kJ
calculate the enthalpy change for the reaction in which methane and oxygen combine to form ketene, CH2CO, and water.
2CH4(g) + 2O2(g) CH2CO(g) + 3H2O(g)H = ? kJ/mol Answer: -623.5kJ/mol
4. Calculate the reaction enthalpy for the following reaction.Is this reaction exothermic or endothermic?
5CO2(g) +Si3N4(s) 3SiO(s) +2N2O(g) + 5CO(g)H = ? kJ/mol Answer:2024 kJ/mol
Use the following equations and data.
CO(g) + SiO2(s) SiO(g) + CO2(g)H = +520.9 kJ
8CO2(g) + Si3N4(s) 3SiO2(s) + 2N2O(g) + 8CO(g) H = +461.05 kJ
5. Calculate H for the reaction of calcium oxide and sulfur trioxide. Is this reaction exothermic or endothermic?
CaO(s) + SO3(g) CaSO4(s) H = ? kJ/mol
Use the following equations and data.
H2O(l) + SO3(g) H2SO4(l) / H = 132.5 kJ/molH2SO4(l) + Ca(s) CaSO4(s) + H2(g) / H = 602.5 kJ/mol
Ca(s) + ½ O2(g) CaO(s) / H = 634.9 kJ/mol
H2(g) + ½ O2(g) H2O(l) / H = 285.8 kJ/mol
6. Find the enthalpy of the reaction of magnesium oxide with hydrogen chloride.
MgO(s) + 2HCl(g) MgCl2(s) + H2O(l)H = ? kJ/mol Answer:-141.1kJ/mol
Use the following equations and data.
Mg(s) + 2HCl(g) MgCl2(s) + H2(g) / H=456.9 kJ/molMg(s) + ½ O2(g) MgO(s) / H = 601.6 kJ/mol
H2O(l) H2(g) + ½ O2(g) / H = +285.8 kJ/mol
7.
Conservation of Energy Problems
8. If a glass of water gains 3050J of energy and turns into water vapor, how much energy, in joules, must the surrounding environmentlose?
9. The molar enthalpy of fusion for bromine is 10.6kJ/mol. Which of the following conversions requires an input of 10.6kJ of heat?
a. one mole of bromine from solid to liquidb. one mole of bromine from liquid to solid
c. one kg of bromine from solid to liquidd. one kg of bromine from liquid to solid
10. A 2.80g piece of metal absorbs 10.0J of energy as it is heated from 22.0°C to 35.0°C. Find the specific heat (in J/g•K) of this metal.
11. The heat released during the combustion of 250.g of propane (C3H8) was 950.kJ. Calculate the molar enthalpy (in kJ/mol) change for the reaction.