The dissociation constant of water is represented by
`K = [H_3O^+][OH^-]/[H_2O]`
`or K_w = [H^+][OH^-]`
`K_w` is called

Options

A. Ionic product of salts
B. Ionic product of water
C. Ionisation constant of water
D. Ionisation constant of acid and base

Answer

To answer the question regarding the dissociation constant of water, we can follow these steps:

### Step 1: Understand the concept of dissociation constant
The dissociation constant of water, often denoted as \( K_w \), is a measure of the extent to which water dissociates into its ions, hydronium ions (\( H_3O^+ \) or \( H^+ \)) and hydroxide ions (\( OH^- \)).

### Step 2: Write the expression for the dissociation of water
The dissociation of water can be represented by the following equation:
\[ H_2O \rightleftharpoons H^+ + OH^- \]
From this reaction, we can derive the expression for the dissociation constant \( K_w \).

### Step 3: Derive the expression for \( K_w \)
The expression for the dissociation constant \( K_w \) is given by:
\[ K_w = \frac{[H^+][OH^-]}{[H_2O]} \]
However, since the concentration of pure water (\( [H_2O] \)) remains constant, we can simplify this to:
\[ K_w = [H^+][OH^-] \]

### Step 4: State the value of \( K_w \)
At 25°C, the value of \( K_w \) is approximately:
\[ K_w = 1.0 \times 10^{-14} \]

### Conclusion
Thus, \( K_w \) is called the dissociation constant of water, and it quantifies the product of the concentrations of hydrogen ions and hydroxide ions in pure water.

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