Question

2. Is the following reaction a redox reaction? Justify your answer by showing the oxidation numbers for each element and show your work. (5 Marks)

S(s) + HNO3 (aq ) → SO2 (g) + NO (g) + H2O (l)

Answer 1

Make it short.

Answer 2

To determine if the reaction

\[ \text{S(s)} + \text{HNO}_3(aq) \rightarrow \text{SO}_2(g) + \text{NO}(g) + \text{H}_2O(l) \]

is a redox reaction, we need to assign oxidation numbers to each element in the reaction and look for changes in these numbers.

### Step 1: Assign Oxidation Numbers
1. **Sulfur (S)** in elemental form (S(s)):
- Oxidation number = 0

2. **HNO3 (aq)**:
- Hydrogen (H) = +1
- Nitrogen (N) = +5
- Oxygen (O) = -2 (there are three oxygens, contributing -6)
- The overall charge is neutral (0), which verifies: +1 + 5 + (-6) = 0.

3. **SO2 (g)**:
- Sulfur (S) = +4
- Oxygen (O) = -2 (there are two oxygens, contributing -4)
- +4 + (-4) = 0, confirming it balances.

4. **NO (g)**:
- Nitrogen (N) = +2
- Oxygen (O) = -2
- +2 + (-2) = 0, confirming it balances.

5. **H2O (l)**:
- Hydrogen (H) = +1 (two hydrogens, contributing +2)
- Oxygen (O) = -2
- +2 + (-2) = 0, confirming it balances.

### Summary of Oxidation Numbers:
- **Reactants**:
- S (0)
- H (1) | N (5) | O (-2) in HNO3

- **Products**:
- S (+4) in SO2
- N (+2) in NO
- H (1) | O (-2) in H2O

### Step 2: Determine Changes in Oxidation Numbers
By comparing the oxidation numbers:

- **Sulfur**:
- Changes from 0 in S(s) to +4 in SO2 (Oxidation, loss of electrons).

- **Nitrogen**:
- Changes from +5 in HNO3 to +2 in NO (Reduction, gain of electrons).

### Step 3: Conclusion
Since oxidation involves an increase in oxidation number (S from 0 to +4), and reduction involves a decrease in oxidation number (N from +5 to +2), we have:

- The oxidation half-reaction: \( S(s) \rightarrow SO_2(g) \)
- The reduction half-reaction: \( HNO_3(aq) \rightarrow NO(g) + \text{other products} \)

Thus, because there are elements undergoing both oxidation and reduction in this reaction, it **is a redox reaction**.

### Final Answer:
Yes, the reaction is a redox reaction, evidenced by the oxidation of sulfur from 0 to +4 and the reduction of nitrogen from +5 to +2.

Answer 3

Yes, the reaction:

\[ \text{S(s)} + \text{HNO}_3(aq) \rightarrow \text{SO}_2(g) + \text{NO}(g) + \text{H}_2O(l) \]

is a redox reaction.

### Oxidation Numbers:
- **S(s)**: 0
- **HNO3**: H (+1), N (+5), O (-2)
- **SO2**: S (+4), O (-2)
- **NO**: N (+2), O (-2)
- **H2O**: H (+1), O (-2)

### Changes:
- **Sulfur**: 0 (in S) → +4 (in SO2) **(oxidation)**
- **Nitrogen**: +5 (in HNO3) → +2 (in NO) **(reduction)**

### Conclusion:
Since sulfur is oxidized and nitrogen is reduced, this is a redox reaction.