For a reaction to occur spontaneously

Options

A. `DeltaS` must be negative
B. `(-DeltaH+T DeltaS)` must be positive
C. `DeltaH + TDeltaS` must be negative
D. `DeltaH` must be negative

Explanation

To determine the conditions under which a chemical reaction occurs spontaneously at all temperatures, we can analyze the Gibbs free energy change (ΔG) for the reaction. The Gibbs free energy change is given by the equation:

\[ \Delta G = \Delta H - T\Delta S \]

Where:
- ΔG = change in Gibbs free energy
- ΔH = change in enthalpy
- T = temperature in Kelvin
- ΔS = change in entropy

### Step-by-Step Solution:

1. **Understanding Spontaneity**:
For a reaction to be spontaneous, the Gibbs free energy change (ΔG) must be negative (ΔG < 0).

2. **Analyzing the Gibbs Free Energy Equation**:
From the equation ΔG = ΔH - TΔS, we can see that ΔG depends on both ΔH and ΔS.

3. **Conditions for ΔG to be Negative**:
- If ΔH is negative (ΔH < 0), this indicates that the reaction is exothermic, which favors spontaneity.
- If ΔS is positive (ΔS > 0), this indicates that the disorder of the system increases, which also favors spontaneity.

4. **Combining the Conditions**:
For ΔG to be negative at all temperatures:
- ΔH must be negative (ΔH < 0).
- ΔS must be positive (ΔS > 0).

This ensures that regardless of the temperature (T), the term -TΔS will always contribute to making ΔG negative.

5. **Conclusion**:
Therefore, the conditions for a chemical process to be spontaneous at all temperatures are:
- ΔH < 0 (Enthalpy change is negative)
- ΔS > 0 (Entropy change is positive)

### Final Answer:
The correct conditions that ensure a chemical process is spontaneous at all temperatures are:
- ΔH < 0
- ΔS > 0