`H^(+)` ion concentration of water does not change by adding:
a.`CH_(3)COONa`
b.`NaNO_(3)`
c.`NaCN`
d. `Na_(2)CO_(3)`

Options

A. `CH_(3)COONa`
B. `NaNO_(3)`
C. `NaCN`
D. `Na_(2)CO_(3)`

Answer

To determine which salt does not change the concentration of \( H^+ \) ions in water, we need to analyze the nature of each salt provided in the options.

### Step-by-Step Solution:

1. **Understanding the pH of Water**:
- Pure water has a neutral pH of 7, which means the concentration of \( H^+ \) ions is \( 1 \times 10^{-7} \) M.

2. **Analyzing Each Salt**:
- **a. \( CH_3COONa \) (Sodium Acetate)**:
- Sodium acetate is a salt formed from a weak acid (acetic acid) and a strong base (sodium hydroxide).
- When dissolved in water, it hydrolyzes to produce \( OH^- \) ions, making the solution basic (pH > 7).
- Therefore, it will change the \( H^+ \) ion concentration.

- **b. \( NaNO_3 \) (Sodium Nitrate)**:
- Sodium nitrate is a salt formed from a strong acid (nitric acid) and a strong base (sodium hydroxide).
- This salt does not hydrolyze in water, meaning it does not affect the \( H^+ \) ion concentration. The solution remains neutral (pH = 7).
- Thus, this salt does not change the \( H^+ \) ion concentration.

- **c. \( NaCN \) (Sodium Cyanide)**:
- Sodium cyanide is a salt formed from a strong base (sodium hydroxide) and a weak acid (hydrogen cyanide).
- It hydrolyzes in water to produce \( OH^- \) ions, resulting in a basic solution (pH > 7).
- Therefore, it will change the \( H^+ \) ion concentration.

- **d. \( Na_2CO_3 \) (Sodium Carbonate)**:
- Sodium carbonate is a salt formed from a strong base (sodium hydroxide) and a weak acid (carbonic acid).
- It also hydrolyzes in water to produce \( OH^- \) ions, making the solution basic (pH > 7).
- Hence, it will change the \( H^+ \) ion concentration.

3. **Conclusion**:
- The only salt that does not change the \( H^+ \) ion concentration of water is **b. \( NaNO_3 \)**.

### Final Answer:
**b. \( NaNO_3 \)**