assignment 5: solved problem 2. the standard heats of formation of c₂h₅oh(l), co₂(g) and h₂o(l) are - 277.0…

assignment 5: solved problem 2. the standard heats of formation of c₂h₅oh(l), co₂(g) and h₂o(l) are - 277.0, - 393.5 and - 285.5 kj mol⁻¹ respectively. calculate the standard heat change for the reaction c₂h₅oh(l)+3o₂(g)→2co₂(g)+3h₂o(l)

assignment 5: solved problem 2. the standard heats of formation of c₂h₅oh(l), co₂(g) and h₂o(l) are - 277.0, - 393.5 and - 285.5 kj mol⁻¹ respectively. calculate the standard heat change for the reaction c₂h₅oh(l)+3o₂(g)→2co₂(g)+3h₂o(l)

Answer

Explanation:

Step1: Recall the formula for $\Delta H^{\circ}_{rxn}$

$\Delta H^{\circ}{rxn}=\sum n\Delta H^{\circ}{f}(products)-\sum m\Delta H^{\circ}_{f}(reactants)$

Step2: Identify $\Delta H^{\circ}_{f}$ values for products

For $CO_2(g)$: $\Delta H^{\circ}{f}(CO_2(g))=- 393.5\ kJ/mol$, and there are 2 moles. For $H_2O(l)$: $\Delta H^{\circ}{f}(H_2O(l))=-285.5\ kJ/mol$, and there are 3 moles. $\sum n\Delta H^{\circ}_{f}(products)=2\times(-393.5)+3\times(-285.5)$ $= - 787-856.5=-1643.5\ kJ/mol$

Step3: Identify $\Delta H^{\circ}_{f}$ values for reactants

For $C_2H_5OH(l)$: $\Delta H^{\circ}{f}(C_2H_5OH(l))=-277.0\ kJ/mol$, and for $O_2(g)$: $\Delta H^{\circ}{f}(O_2(g)) = 0\ kJ/mol$ (standard - state element), and there are 3 moles of $O_2$. $\sum m\Delta H^{\circ}_{f}(reactants)=-277.0+3\times0=-277.0\ kJ/mol$

Step4: Calculate $\Delta H^{\circ}_{rxn}$

$\Delta H^{\circ}_{rxn}=-1643.5-(-277.0)$ $=-1643.5 + 277.0=-1366.5\ kJ/mol$

Answer:

$-1366.5\ kJ/mol$