Which of the following statements is incorrect?

Options

A. `H_(2)O_(2)` is a pale blue viscous liquid
B. `H_(2)O_(2)` ca act as an oxidising as well as a reducing agent
C. In `H_(2)O_(2)`, the two hydroxyl groups lie on the same plane.
D. `H_(2)O_(2)` has an 'open-book' structure

Answer

To determine which statement about H2O2 (hydrogen peroxide) is incorrect, we will analyze each option provided.

### Step-by-Step Solution:

1. **Statement A: H2O2 is a pale blue color viscous liquid.**
- **Analysis**: This statement is true. Hydrogen peroxide is indeed a pale blue liquid and has a viscous nature.

2. **Statement B: H2O2 acts as both an oxidizing and reducing agent.**
- **Analysis**: This statement is also true. Hydrogen peroxide can act as an oxidizing agent (when it gains electrons) and as a reducing agent (when it loses electrons) due to the variable oxidation states of oxygen in its structure.

3. **Statement C: In H2O2, the two hydroxyl groups lie in the same plane.**
- **Analysis**: This statement is incorrect. The structure of hydrogen peroxide is often described as an "open book" structure, where the two hydroxyl (–OH) groups are not in the same plane but are positioned in different planes.

4. **Statement D: H2O2 has an open book structure.**
- **Analysis**: This statement is true. The molecular structure of hydrogen peroxide is indeed described as an open book structure, with the two hydroxyl groups positioned in a way that they do not lie in the same plane.

### Conclusion:
The incorrect statement among the options is **Statement C**: "In H2O2, the two hydroxyl groups lie in the same plane."