In general, for exothermic reactions to be spontaneous

Options

A. temperature should be high
B. temperature should be zero
C. temperature should be low
D. temperature has no effect

Explanation

To determine the conditions under which exothermic reactions are spontaneous, we need to analyze the relationship between enthalpy change (ΔH), entropy change (ΔS), and temperature (T) using the Gibbs free energy equation:

### Step-by-Step Solution:

1. **Understand the Gibbs Free Energy Equation**:
The spontaneity of a reaction can be determined using the Gibbs free energy equation:
\[ \Delta G = \Delta H - T \Delta S \]
where ΔG is the change in Gibbs free energy, ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.

2. **Identify the Nature of the Reaction**:
For exothermic reactions, ΔH is negative (ΔH < 0). This means that the reaction releases heat.

3. **Consider the Role of Entropy (ΔS)**:
The sign of ΔS (positive or negative) will influence the spontaneity of the reaction.
- If ΔS is positive (the disorder of the system increases), the reaction is more likely to be spontaneous at any temperature.
- If ΔS is negative (the disorder of the system decreases), the spontaneity will depend on the temperature.

4. **Analyze the Conditions for Spontaneity**:
- For ΔG to be negative (indicating spontaneity), we can rearrange the Gibbs free energy equation:
\[ \Delta G < 0 \implies \Delta H - T \Delta S < 0 \]
- Rearranging gives:
\[ T \Delta S > \Delta H \]
- If ΔS is negative, increasing T can make it harder for the reaction to be spontaneous. Thus, lower temperatures favor exothermic reactions with negative ΔS.

5. **Conclusion**:
Since we know that ΔH is negative for exothermic reactions, and without specific information about ΔS, we can conclude that exothermic reactions are favored by low temperatures. Therefore, the correct answer is:
- **Temperature should be low**.

### Final Answer:
The correct option is: **Temperature should be low (Option C)**.

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