When a copper vessel is exposed to moist air for long, it acquires a dull green coating. The reaction can be represented as
`2Cu+underset("moist air")ubrace(W+X+Y) to Cu(OH)_(2)+Z`
W,X,Y and Z respectively

Explanation

To solve the problem, we need to identify the components of the reaction when copper (Cu) is exposed to moist air, which leads to the formation of a dull green coating. The reaction can be represented as:

\[ 2Cu + W + X + Y \rightarrow Cu(OH)_2 + Z \]

### Step-by-Step Solution:

1. **Identify the Components of Moist Air**:
- Moist air consists of water vapor (H₂O), carbon dioxide (CO₂), and oxygen (O₂). Thus, we can denote:
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