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If you need to reverse the following reaction for a Hess's law problem, what would be the final value for the enthalpy of reaction?

[tex]\[
H_2 + 0.5 O_2 \rightarrow H_2O , \Delta H = -286 \, \text{kJ}
\][/tex]

A. [tex]\( 286 \, \text{kJ} \)[/tex]
B. [tex]\( 572 \, \text{kJ} \)[/tex]
C. [tex]\( -572 \, \text{kJ} \)[/tex]
D. [tex]\( -286 \, \text{kJ} \)[/tex]



Answer :

GinnyAnswer
To solve this problem, we need to reverse the given chemical reaction and determine the enthalpy change for the reversed reaction. Let's analyze step-by-step:

1. Understand the Original Reaction and its Enthalpy Change:
- The given reaction is:
[tex]\[ H_2 + 0.5 O_2 \rightarrow H_2O \][/tex]
- The enthalpy change ([tex]\(\Delta H\)[/tex]) for this reaction is [tex]\(-286 \, \text{kJ}\)[/tex].

2. Reverse the Reaction:
- Reversing the reaction means flipping the reactants and products:
[tex]\[ H_2O \rightarrow H_2 + 0.5 O_2 \][/tex]

3. Determine the New Enthalpy Change:
- When reversing a chemical reaction, the sign of the enthalpy change also reverses. The original reaction had an enthalpy change of [tex]\(-286 \, \text{kJ}\)[/tex].
- Reversing the reaction changes the sign of [tex]\(\Delta H\)[/tex]:
[tex]\[ \Delta H_{reversed} = -(-286 \, \text{kJ}) = 286 \, \text{kJ} \][/tex]

Thus, the enthalpy change for the reversed reaction is [tex]\(286 \, \text{kJ}\)[/tex].

4. Select the Correct Answer:
- Among the given choices, the correct answer is:
[tex]\[ \text{A. } 286 \, \text{kJ} \][/tex]

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