How many is the following reaction (s) have sum of co-efficient of reactants after balancing either 3 or 4.

Options

A. `FeSO_(4)toFe_(2)O_(3)+SO_(2)+SO_(3)`
B. `Br_(2)+barOHtoBrO^(-)+Br^(-)+H_(2)O`
C. `Cl_(2)+SeO_(3)^(2-)+H_(2)OtoSeO_(4)^(2-)+Cl^(-)+H^(+)`
D. `Cl_(2)+IO_(3)^(-)+OH^(-)toCl^(-)+IO_(4)^(-)+H_(2)O`

Explanation

To solve the problem of how many of the given reactions have a sum of coefficients of the reactants after balancing that is either 3 or 4, we will analyze each reaction step by step.

### Step 1: Analyze the first reaction
**Reaction**: \( \text{FeSO}_4 \rightarrow \text{Fe}_2\text{O}_3 + \text{SO}_2 + \text{SO}_3 \)

1. **Identify the reactants**:
- \( \text{FeSO}_4 \) (1 coefficient)

2. **Identify the products**:
- \( \text{Fe}_2\text{O}_3 \) (1 coefficient)
- \( \text{SO}_2 \) (1 coefficient)
- \( \text{SO}_3 \) (1 coefficient)

3. **Balancing the reaction**:
- To balance Fe: \( 2 \text{FeSO}_4 \rightarrow \text{Fe}_2\text{O}_3 + \text{2SO}_2 + \text{SO}_3 \)
- Now, we have:
- **Fe**: 2 on both sides
- **S**: 2 on the left, 3 on the right (needs adjustment)
- **O**: 8 on the left, 9 on the right (needs adjustment)

4. **Final balanced equation**:
- \( 4 \text{FeSO}_4 \rightarrow 2 \text{Fe}_2\text{O}_3 + 6 \text{SO}_2 + 2 \text{SO}_3 \)
- **Sum of coefficients of reactants**: \( 4 \) (from \( 4 \text{FeSO}_4 \))

### Step 2: Analyze the second reaction
**Reaction**: \( \text{Br}_2 + \text{OH}^- \rightarrow \text{BrO}^- + \text{Br}^- + \text{H}_2\text{O} \)

1. **Identify the reactants**:
- \( \text{Br}_2 \) (1 coefficient)
- \( \text{OH}^- \) (1 coefficient)

2. **Balancing the reaction**:
- \( \text{Br}_2 + 2 \text{OH}^- \rightarrow 2 \text{BrO}^- + \text{H}_2\text{O} \)
- **Sum of coefficients of reactants**: \( 1 + 2 = 3 \)

### Step 3: Analyze the third reaction
**Reaction**: \( \text{Cl}_2 + \text{Se}^{2-} + \text{H}_2\text{O} \rightarrow \text{SeO}_4^{2-} + 2 \text{Cl}^- + 2 \text{H}^+ \)

1. **Identify the reactants**:
- \( \text{Cl}_2 \) (1 coefficient)
- \( \text{Se}^{2-} \) (1 coefficient)
- \( \text{H}_2\text{O} \) (1 coefficient)

2. **Balancing the reaction**:
- \( \text{Cl}_2 + \text{Se}^{2-} + 2 \text{H}_2\text{O} \rightarrow \text{SeO}_4^{2-} + 2 \text{Cl}^- + 2 \text{H}^+ \)
- **Sum of coefficients of reactants**: \( 1 + 1 + 2 = 4 \)

### Step 4: Analyze the fourth reaction
**Reaction**: \( \text{Cl}_2 + \text{IO}_3^- + \text{OH}^- \rightarrow \text{Cl}^- + \text{IO}_4^- + \text{H}_2\text{O} \)

1. **Identify the reactants**:
- \( \text{Cl}_2 \) (1 coefficient)
- \( \text{IO}_3^- \) (1 coefficient)
- \( \text{OH}^- \) (1 coefficient)

2. **Balancing the reaction**:
- \( 2 \text{Cl}_2 + 2 \text{IO}_3^- + 2 \text{OH}^- \rightarrow 2 \text{Cl}^- + 2 \text{IO}_4^- + 2 \text{H}_2\text{O} \)
- **Sum of coefficients of reactants**: \( 2 + 2 + 2 = 6 \) (not applicable)

### Conclusion
After analyzing all reactions:
- The reactions with a sum of coefficients of reactants equal to either 3 or 4 are:
- **Second reaction**: Sum = 3
- **Third reaction**: Sum = 4

Thus, the answer is that **2 reactions** have a sum of coefficients of reactants either 3 or 4.