Give reason for each of the following:
In the contact process of manufacture of sulphuric acid, the oxide of arsenic is removed. 

Explanation

### Step-by-Step Solution:

1. **Understanding the Contact Process**: The contact process is the method used to manufacture sulfuric acid (H₂SO₄) from sulfur dioxide (SO₂). This process involves several steps, including the oxidation of sulfur dioxide to sulfur trioxide (SO₃) and the subsequent absorption of SO₃ in water to form sulfuric acid.

2. **Role of Catalysts**: In the contact process, catalysts are used to speed up the reaction between sulfur dioxide and oxygen. Historically, platinum was used as a catalyst, but currently, vanadium pentoxide (V₂O₅) is the preferred catalyst due to its effectiveness and lower cost.

3. **Presence of Arsenic Oxide**: During the production of sulfur dioxide, impurities such as arsenic oxide (As₂O₃) can be formed. This impurity can enter the contact process along with the sulfur dioxide gas.

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