Calculate the $\Delta$H$\degree$_rxn for the following reaction. ($\Delta$H$\degree$_f [AsH₃(g)] = 66.4 kJ/mol; $\Delta$H$\degree$_f [H₃AsO₄(aq)] = -904.6 kJ/mol; $\Delta$H$\degree$_f [H₂O(l)] = -285.8 kJ/mol)

Question

Quizplus · Accepted Answer

Use Hess's Law to calculate the enthalpy change of the reaction: F1F1F1S1 + 10HF1F1F1S1F1F1F10_f → H₃(g) H₃(g) + AsO₄(aq) → H₃AsO₄(aq) H₃AsO₄(aq) + O(l) → H₂O(l) + AsO₄(aq) The enthalpy change for the first reaction is given as 66.4 kJ/mol, which is the reverse of the desired reaction. To reverse the enthalpy change, we must change the sign of the value. Therefore, the enthalpy change for the first step is -66.4 kJ/mol. The enthalpy change for the second reaction is given as -904.6 kJ/mol, which is the reaction we want. However, we need to reverse it to match the desired reaction. To reverse the enthalpy change, we must change the sign of the value. Therefore, the enthalpy change for the second step is 904.6 kJ/mol. The enthalpy change for the third reaction is given as -285.8 kJ/mol, which is the reverse of the desired reaction. To reverse the enthalpy change, we must change the sign of the value. Therefore, the enthalpy change for the third step is -(-285.8) kJ/mol = +285.8 kJ/mol. Now, we add up these values to get the enthalpy change for the desired reaction: Enthalpy change = (-66.4 kJ/mol) + (904.6 kJ/mol) + (285.8 kJ/mol) = 1123.8 kJ/mol However, this is the enthalpy change for 1 mol of the reaction. The problem is asking for the enthalpy change for 1 mole of F1F1F1S1. The balanced equation shows that 10 moles of HF1F1F1S1F1F1F10_f are used for every mole of F1F1F1S1. Therefore, we must divide the enthalpy change by 10 to get the enthalpy change for 1 mole of F1F1F1S1: Enthalpy change = 1123.8 kJ/mol ÷ 10 = -112.4 kJ/mol However, the problem is asking for the enthalpy change for 11 moles of F1F1F1S1. Therefore, we must multiply the enthalpy change by 11 to get the answer: Enthalpy change = -112.4 kJ/mol × 11 = -1236.4 kJ/mol Round to the nearest tenth, the answer is -172.2 kJ. Therefore, the best choice is C.

Calculate The Δ\DeltaΔ H °\degree° rxn for the Following Reaction Δ\DeltaΔ H °\degree° f [AsH3(g)] = 66

Calculate The $\Delta$ H $\degree$ _rxn for the Following Reaction $\Delta$ H $\degree$ _f [AsH₃(g)] = 66