Oxygen is obtained by heating

Options

A. ammonium dichromate
B. sodium peroxide
C. potassium permagnate
D. green vitrol

Explanation

To determine which compound produces oxygen gas upon heating, we can analyze the reactions of the given compounds. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Compounds
The compounds mentioned are:
1. Ammonium dichromate (NH4)2Cr2O7
2. Sodium peroxide (Na2O2)
3. Potassium permanganate (KMnO4)
4. Green vitriol (FeSO4·7H2O)

### Step 2: Analyze Ammonium Dichromate
When ammonium dichromate is heated, it decomposes to produce:
- Chromic oxide (Cr2O3)
- Water (H2O)
- Nitrogen gas (N2)

**Reaction**:
\[ (NH_4)_2Cr_2O_7 \rightarrow Cr_2O_3 + 4H_2O + N_2 \]
**Conclusion**: No oxygen gas is produced.

### Step 3: Analyze Sodium Peroxide
Sodium peroxide undergoes a structural transition upon heating but does not release oxygen gas. It simply changes its symmetry and structure.

**Conclusion**: No oxygen gas is produced.

### Step 4: Analyze Potassium Permanganate
When potassium permanganate is heated, it decomposes to produce:
- Potassium manganate (K2MnO4)
- Manganese dioxide (MnO2)
- Oxygen gas (O2)

**Reaction**:
\[ 2KMnO_4 \rightarrow K_2MnO_4 + MnO_2 + O_2 \]
**Conclusion**: Oxygen gas is produced.

### Step 5: Analyze Green Vitriol
Green vitriol (ferrous sulfate) when heated releases water and forms anhydrous ferrous sulfate but does not produce oxygen gas.

**Reaction**:
\[ FeSO_4 \cdot 7H_2O \rightarrow FeSO_4 + 7H_2O \]
**Conclusion**: No oxygen gas is produced.

### Final Conclusion
Among the compounds analyzed, only potassium permanganate (KMnO4) produces oxygen gas upon heating.

### Answer
**Oxygen is obtained by heating potassium permanganate (KMnO4).**

---