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Help with Standard Enthalpy Change Calculation?

Calculate the standard enthalpy change of the reaction ClO(g) + O3(g) ---> ClO2(g) = 02(g)
Standard enthalpies are: ClO(g) is 101; for O3 is 142.3; for O2 is 0; for O(g), is 247.5.

2 Answers

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Final answer:

To calculate the standard enthalpy change of the given reaction, you can use Hess's Law to add the known enthalpy changes of two equations that can be combined to give the desired equation. Reverse Equation 1 to obtain 2 CO(g) → 2 C(s) + O2(g) with a ΔH = +221.0 kJ, and use Equation 2 as written: C(s) + O2(g) → CO2(g) with a ΔH = -393.5 kJ. Adding these equations will give the standard enthalpy change of the reaction.

Step-by-step explanation:

To calculate the standard enthalpy change of the given reaction ClO(g) + O3(g) → ClO2(g) + O2(g), you can use the Hess's Law. First, you need to write two equations that can be added together to give the desired equation and for which the enthalpy changes are known. You can reverse the direction of the reaction in Equation 1 to obtain 2 CO(g) → 2 C(s) + O2(g) with a ΔH = +221.0 kJ. Then, you can use Equation 2 as written because its product, CO2, is the product we want in Equation 3: C(s) + O2(g) → CO2(g) with a ΔH = -393.5 kJ. Adding these two equations gives you the desired reaction, and you can sum up the enthalpy changes to calculate the standard enthalpy change of the reaction.

User Evolutionxbox
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We substitute the enthalpies for the reactants in the equation:
101 + 142.3 = ΔH + 247.5
ΔH = -4.2 kJ/mol
User Kris Nuttycombe
by
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