Mercuic oxide and curpic oxide both gives offf oxygen on moderate heating.

Explanation

To determine whether the statement "Mercuric oxide and cupric oxide both give off oxygen on moderate heating" is true or false, we will analyze the decomposition reactions of both mercuric oxide (HgO) and cupric oxide (CuO) when heated.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Mercuric oxide is represented as HgO.
- Cupric oxide is represented as CuO.

2. **Decomposition of Mercuric Oxide (HgO)**:
- When mercuric oxide is heated, it decomposes into mercury and oxygen gas.
- The chemical equation for this reaction is:
\[ 2 \text{HgO} \rightarrow 2 \text{Hg} + \text{O}_2 \]
- From this equation, we can see that oxygen gas (O₂) is indeed evolved when mercuric oxide is heated.

3. **Decomposition of Cupric Oxide (CuO)**:
- When cupric oxide is heated, it does not decompose to release oxygen gas. Instead, it is reduced to cuprous oxide (Cu₂O).
- The chemical equation for this reaction can be represented as:
\[ 2 \text{CuO} \rightarrow \text{Cu}_2\text{O} + \text{O}_2 \]
- However, in this case, cupric oxide does not release oxygen gas; rather, it is converted into another oxide (cuprous oxide) without evolving oxygen.

4. **Conclusion**:
- Since mercuric oxide releases oxygen when heated, but cupric oxide does not release oxygen, the statement "Mercuric oxide and cupric oxide both give off oxygen on moderate heating" is **false**.

### Final Answer:
The statement is **false**.