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# Thermochemistry Practice Questions

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Review the following concepts if needed -  Thermochemistry Study Guide

## Practice Problems

 1 Calculate the energy released when a 4,570 g piece of hot iron cools from 1000° C to 20° C. 2 Calculate the energy needed to heat 60 g of aluminum from 100° C to 250° C. 3 Calculate the final temperature of 295 g of water, initially at 30.0° C, if 4,500 joules are added.

Calculate the standard enthalpy of reaction for the following reactions (don't forget to balance the equations first!). Also, indicate whether the reaction is exothermic or endothermic.

 4 C2H6(g) + O2(g) → H2O(g) + CO2(g) (combustion of ethane) 5 H2O(l) + CO2(g) → C6H12O6(s) +O2(g) (photosynthesis) 6 SO2(g) + O2(g) → SO3(g) 7 Fe(s) + O2(g) → Fe2O3(s) (oxidation of iron)

 8.Calculate the enthalpy change for P4(s) + 6Cl2(g) → 4PCl3(l) given P4(s) + 10Cl2(g) → 4PCl5(s) ΔH = –1774.0 kJ PCl3(l) + Cl2(g) → PCl5(s) ΔH = –123.8 kJ 9.Calculate the enthalpy change for 2B(s) + 3H2(g)→ B2H6(g), given 4B(s) + 3O2(g) → 2B2O3(g) ΔH = –2546 kJ B2H6(g) + 3O2(g) → 2B2O3(g) + 3H2O (g) ΔH = – 2035 kJ H2O(l) → H2O(g) ΔH = 44kJ

 1 –2.02 * 106 J = –2020 kJ 2 8,010 J = 8.01 kJ 3 33.6° C 4 – 1,428 kJ, exothermic 5 2,802 kJ, endothermic 6 –89 kJ, exothermic 7 v826 kJ, exothermic 8 –1,774.0 kJ 9 +36 kJ

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