Calculate ΔH for the reaction Zn(s)+(1)/(2) O2( g) →ZnO(s) ΔH=? given the equations Zn(s)+2 H

step 1 In this question we're going to be looking at three equations where the first equation we've got

Calculate ΔH for the reaction Zn(s)+(1)/(2) O2( g) →ZnO(s) ...

Calculate $\Delta H$ for the reaction $$ \mathrm{Zn}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{ZnO}(\mathrm{s}) \quad \Delta H=? $$ given the equations $$ \begin{aligned} \mathrm{Zn}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{ZnCl}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g}) & \Delta H=-152.4 \mathrm{~kJ} \\ \mathrm{ZnO}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{ZnCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell) \\ \Delta H=-90.2 \mathrm{~kJ} \\ 2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\ell) & \Delta H=-571.6 \mathrm{~kJ} \end{aligned} $$

Calculate $\Delta H$ for the reaction
$$
\mathrm{Zn}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{ZnO}(\mathrm{s}) \quad \Delta H=?
$$
given the equations
$$
\begin{aligned}
\mathrm{Zn}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{ZnCl}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g}) & \Delta H=-152.4 \mathrm{~kJ} \\
\mathrm{ZnO}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{ZnCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell) \\
\Delta H=-90.2 \mathrm{~kJ} \\
2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\ell) & \Delta H=-571.6 \mathrm{~kJ}
\end{aligned}
$$

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Key Concepts

Hess's Law

Hess's law is a principle that states the total enthalpy change for a reaction is the same regardless of the pathway taken, as long as the reaction starts and ends in the same chemical states. This idea allows us to add or subtract chemical equations to calculate the overall enthalpy change.

Enthalpy as a State Function

Enthalpy is a state function, meaning its value depends only on the initial and final states of a system and not on the path taken. This property ensures that when combining reactions through Hess's law, the calculated overall enthalpy change is accurate regardless of the intermediate steps.

Manipulation of Chemical Equations

When using Hess's law, chemical equations can be algebraically manipulated by reversing, scaling, and adding equations. Reversing a reaction changes the sign of its enthalpy, and scaling a reaction by a factor multiplies its enthalpy change by the same factor, allowing for proper cancellation of species to match the overall reaction.

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