Which of the following will not liberate dihydrogen ?

Options

A. `Zn + H_(2)SO_(4)` (di.)
B. `Zn + NaOH(aq)`
C. `Cu + H_(2)SO_(4)`(conc.)
D. `F_(2) + H_(2)O`

Answer

To determine which of the given reactions will not liberate dihydrogen (H₂), we will analyze each reaction step-by-step.

### Step 1: Analyze the first reaction
**Reaction:** Zinc + Dilute H₂SO₄
**Products:** Zinc sulfate (ZnSO₄) + Hydrogen gas (H₂)
**Conclusion:** This reaction liberates hydrogen gas.

### Step 2: Analyze the second reaction
**Reaction:** Zinc + Aqueous NaOH
**Products:** Sodium zincate (Na₂ZnO₂) + Hydrogen gas (H₂)
**Conclusion:** This reaction also liberates hydrogen gas.

### Step 3: Analyze the third reaction
**Reaction:** Copper + Concentrated H₂SO₄
**Products:** No reaction occurs.
**Reason:** Copper is less reactive than hydrogen in the reactivity series, meaning it cannot displace hydrogen from sulfuric acid.
**Conclusion:** This reaction does not liberate hydrogen gas.

### Step 4: Analyze the fourth reaction
**Reaction:** Fluorine + Water
**Products:** Hydrofluoric acid (HF) + Oxygen gas (O₂)
**Conclusion:** This reaction produces oxygen gas and does not liberate hydrogen gas.

### Final Conclusion
From the analysis, the reactions that do not liberate dihydrogen are:
- Copper + Concentrated H₂SO₄ (3rd reaction)
- Fluorine + Water (4th reaction)

Thus, the answer to the question is that the third and fourth reactions will not liberate dihydrogen.

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