27. When 0.0500 mol of CH4 (g) burns, 40.1 kJ of heat is produced. What is the change in enthalpy (AH) in kJ for the following reaction: CH4 (g) + 202 (g) (a) +802 kJ/mol (b) -802 kJ/mol , CO₂ (g) + 2H₂O(g) + Heat (c) +40.1 kJ/mol (d) -40.1 kJ/mol
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
![### Example Problem: Calculating Enthalpy Change (ΔH)
**Problem:**
When 0.0500 mol of CH₄(g) burns, 40.1 kJ of heat is produced. What is the change in enthalpy (ΔH) in kJ for the following reaction?
\[
\text{CH}_4(\text{g}) + 2\text{O}_2(\text{g}) \longrightarrow \text{CO}_2(\text{g}) + 2\text{H}_2\text{O}(\text{g}) + \text{Heat}
\]
**Options:**
- (a) +802 kJ/mol
- (b) -802 kJ/mol
- (c) +40.1 kJ/mol
- (d) -40.1 kJ/mol
**Solution:**
Given:
- Heat produced by 0.0500 mol of CH₄(g) = 40.1 kJ
To find the ΔH for the reaction, we need to determine the heat produced per mole of CH₄(g).
1. Calculate heat produced per mole of CH₄(g):
\[
\text{Heat per mole} = \frac{\text{Total heat produced}}{\text{amount in moles}}
\]
\[
\text{Heat per mole} = \frac{40.1 \text{ kJ}}{0.0500 \text{ mol}}
\]
2. Perform the calculation:
\[
\text{Heat per mole} = \frac{40.1}{0.0500} = 802 \text{ kJ/mol}
\]
Since heat is produced, the enthalpy change (ΔH) is negative (exothermic reaction).
**Therefore, the correct answer is:**
- **(b) -802 kJ/mol**
### Explanation:
This calculation is essential in understanding the thermodynamics of chemical reactions. The negative sign indicates that energy is released to the surroundings when methane (CH₄) combusts.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa8713e9b-73ac-4e4f-a322-df330d573c40%2Ff26a4bce-6a16-4135-8da9-6e54f969694e%2Fuxwbv1r_processed.jpeg&w=3840&q=75)
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