Question

): 4,7 10. Given the thermochemical equation Cal) 02/2) + H12) - Ca(OH --49345 kJ/mol-nun find AH for the following reaction Ca(OH)20) -- Calo) + O2(g) + H2(8) a.986.9 kJ/mol-pan b. -986.9 kJ/mol-nxn C.-139 kJ/mol-ran d. -2320 kJ/mol-nun c.-39.7 kJ/mol-ran 11. A hot piece of iron is dropped into a beaker containing colder water. Which of the following statements is/are CORRECT? 1. Energy is transferred as heat from the iron to the water. 7 Thermal equilibrium is attained when the iron and the water reach the same temperature 3. Thermal energy from the iron is converted to clectrostatic energy in the water. a. I only b. 2 only c. 3 only d. 1 and 2 c. 1, 2, and 3

Answer 1

10. According to Hess' law, whatever operations we perform on the reaction, we perform the same operations on ∆Hf.

The required reaction is obtained by multiplying the given reaction by 2 and reversing it. Hence,∆Hf should be multiplied by 2 and the sign should be reversed.

∆Hf for the reaction = 493.45*2 = 986.9 kJ/mol-rxn

Answer: a)