Equivalent weight of `As_(2)O_3` in the following equation `As_(2)O_3 +2I_(2) + 2H_(2)O rarr As_(2)O_(5) +4HI` [arsenic at wt. = 75]

Options

A. 49.5
B. 156.6
C. 94
D. 75

Explanation

To find the equivalent weight of \( As_2O_3 \) in the given reaction:

\[ As_2O_3 + 2I_2 + 2H_2O \rightarrow As_2O_5 + 4HI \]

we will follow these steps:

### Step 1: Determine the oxidation states of arsenic in \( As_2O_3 \) and \( As_2O_5 \)

1. **For \( As_2O_3 \)**:
- Let the oxidation state of arsenic be \( x \).
- The formula can be set up as follows:
\[ 2x + 3(-2) = 0 \]
- This simplifies to:
\[ 2x - 6 = 0 \implies 2x = 6 \implies x = +3 \]
- Thus, the oxidation state of arsenic in \( As_2O_3 \) is \( +3 \).

2. **For \( As_2O_5 \)**:
- Again, let the oxidation state of arsenic be \( x \).
- The formula can be set up as follows:
\[ 2x + 5(-2) = 0 \]
- This simplifies to:
\[ 2x - 10 = 0 \implies 2x = 10 \implies x = +5 \]
- Thus, the oxidation state of arsenic in \( As_2O_5 \) is \( +5 \).

### Step 2: Calculate the change in oxidation state

- The change in oxidation state per arsenic atom is:
\[ +5 - (+3) = +2 \]
- Since there are 2 arsenic atoms in \( As_2O_3 \), the total change in oxidation state for both arsenic atoms is:
\[ 2 \times 2 = 4 \]

### Step 3: Calculate the molecular weight of \( As_2O_3 \)

- The molecular weight of \( As_2O_3 \) can be calculated as follows:
- Atomic weight of arsenic (As) = 75 g/mol
- Atomic weight of oxygen (O) = 16 g/mol
- Therefore, the molecular weight of \( As_2O_3 \) is:
\[ (2 \times 75) + (3 \times 16) = 150 + 48 = 198 \text{ g/mol} \]

### Step 4: Calculate the equivalent weight of \( As_2O_3 \)

- The formula for equivalent weight is:
\[ \text{Equivalent weight} = \frac{\text{Molecular weight}}{\text{Number of electrons transferred}} \]
- Substituting the values:
\[ \text{Equivalent weight} = \frac{198 \text{ g/mol}}{4} = 49.5 \text{ g/equiv} \]

### Conclusion

The equivalent weight of \( As_2O_3 \) in the given reaction is **49.5 g/equiv**.

---