Which one of the following pairs of reactants does not form oxygen when they react with each other?

Options

A. `F_2, NaOH` solution (hot, conc)
B. `F_2, H_2O`
C. `Cl_2, NaOH` solution (cold, dilute)
D. `CaOCl_2, H_2SO_4` (dilute, small amount)

Answer

To determine which pair of reactants does not form oxygen when they react with each other, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Reactants in Each Option**:
- Option 1: Fluorine (F2) + Sodium Hydroxide (NaOH)
- Option 2: Fluorine (F2) + Water (H2O)
- Option 3: Chlorine (Cl2) + Sodium Hydroxide (NaOH)
- Option 4: Calcium Hypochlorite (Ca(OCl)2) + Sulfuric Acid (H2SO4)

2. **Analyze Option 1**:
- Reaction: \( 10F_2 + 20NaOH \rightarrow 20NaF + 10H_2O + O_2 \)
- Conclusion: Oxygen is produced in this reaction.

3. **Analyze Option 2**:
- Reaction: \( F_2 + 2H_2O \rightarrow O_2 + 4F^- + 4H^+ \)
- Conclusion: Oxygen is produced in this reaction.

4. **Analyze Option 3**:
- Reaction: \( Cl_2 + 2NaOH \rightarrow NaCl + NaOCl + H_2O \)
- Conclusion: No oxygen gas is produced in this reaction.

5. **Analyze Option 4**:
- Reaction: \( Ca(OCl)_2 + H_2SO_4 \rightarrow CaCl_2 + CaSO_4 + 2HClO \)
- Breakdown of \( HClO \): It can decompose to produce hydrochloric acid and nascent oxygen.
- Conclusion: Oxygen is ultimately released in this reaction.

6. **Final Conclusion**:
- The only pair of reactants that does not produce oxygen when they react is **Option 3: Chlorine and Sodium Hydroxide**.

### Final Answer:
**Option 3: Chlorine (Cl2) + Sodium Hydroxide (NaOH)** does not form oxygen when they react with each other.