Question

The oxidation number of As in \(\text{H}_{3}\text{AsO}_{3}\).

Answer 1

To determine the oxidation number of arsenic (As) in \(\text{H}_3\text{AsO}_3\), we can follow these steps:

1. **Identify the elements and their known oxidation states**:
- Hydrogen (H) typically has an oxidation state of +1.
- Oxygen (O) typically has an oxidation state of -2.

2. **Set up the equation**:
In \(\text{H}_3\text{AsO}_3\), let the oxidation state of arsenic (As) be \(x\). The compound contains 3 hydrogen atoms, 3 oxygen atoms, and 1 arsenic atom.

3. **Calculate the total oxidation states**:
The total oxidation state for the compound must equal 0 since it is a neutral molecule:
\[
3 \times (+1) + x + 3 \times (-2) = 0
\]

4. **Solve the equation**:
\[
3 - 6 + x = 0
\]
\[
x - 3 = 0
\]
\[
x = +3
\]

Thus, the oxidation number of arsenic (As) in \(\text{H}_3\text{AsO}_3\) is +3.