Use Hess\'s Law to calculate the enthalpy change for the reaction WO_3(s) + 3H_2

Question

Use Hess's Law to calculate the enthalpy change for the reaction WO_3(s) + 3H_2(g) rightarrow W(s) + 3H_2O(g) from the following data: 2W(s) + 3O_3(g) rightarrow 2o_3(S) Delta H = -1685 kJ 2H_2(g) + O_2(g) rightarrow 2H_2O(g) Delta H = -477.84 kJ A)364.9 kJ B) 252.9 kJ C) 1207.6 kJ D) 125.9 kJ E) none of the above Calculate the Delta H_rxn degree for the following reaction. (Delta H degree f [As H_3(g)] = 66.4 kJ/mol; Delta H degree f [H_3As 0_4(eq)] = -904.6 kJ/mol; Delta H degree f [H_2O(l)] = -285 8 kJ/mol) H_3 As O_4(eq) + 4H_2(g) rightarrow As H_3(g) + 4H_2O(l) A) 685.2 kJ B) -1981.4 kJ C) 172.2 kJ D)-685.2 kJ E) -172.2 kJ Calculate Delta S degree for the combustion of propane. C_3 H_8(g) + 5O_2(g) rightarrow 3CO_2(g) + 4H_2O(g) A)-72.5 J/K B) -100.9 J/K C) 72.5J/K D) 100.9 J/K E) 877.5 J/K Calculate Delta G degree for the combustion of propane. C_3H_8(g) + 5O_2(g) rightarrow 3CO_2(g) + 4H_2O(g) A) 598 5 kJ B)-1387.3 kJ C) 598.5 kJ D)-2073.1

Explanation / Answer

4)

let us number the equation as 1,2,3 from top to bottom as given

we need to find H1 using H2 and H3

eqn 1 can be written as

eqn 1 = 1.5*eqn 3 - 0.5*eqn 2

so,

H1 = H3 - 0.5*H2

= (-477.84) - 0.5 * (-1685.4)

= 364.9 KJ

Answer: A

I am allowed to answer only 1 question at a time

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