Which one of the following solutions with same concentrations will have lowest pH?
`NaHCO_(3)`
HCl
KOH
`Na_(2)CO_(3)`

Options

A. `NaHCO_(3)`
B. HCl
C. KOH
D. `Na_(2)CO_(3)`

Answer

To determine which solution has the lowest pH among the given options, we need to analyze each solution based on its acidic or basic nature.

### Step-by-Step Solution:

1. **Identify the nature of each compound:**
- **NaHCO₃ (Sodium Bicarbonate):** This is a salt derived from a weak acid (H₂CO₃) and a strong base (NaOH). It acts as a weak base in solution.
- **HCl (Hydrochloric Acid):** This is a strong acid that completely dissociates in water, producing a high concentration of H⁺ ions.
- **KOH (Potassium Hydroxide):** This is a strong base that completely dissociates in water, producing a high concentration of OH⁻ ions.
- **Na₂CO₃ (Sodium Carbonate):** This is a salt derived from a weak acid (H₂CO₃) and a strong base (NaOH). It also acts as a weak base in solution.

2. **Determine the pH of each solution:**
- **HCl:** Since HCl is a strong acid, it will produce a high concentration of H⁺ ions, leading to a low pH. The pH of a strong acid is typically below 7.
- **NaHCO₃ and Na₂CO₃:** Both are weak bases, and their pH will be above 7, but lower than that of strong bases like KOH.
- **KOH:** As a strong base, KOH will produce a high concentration of OH⁻ ions, resulting in a high pH, typically above 14.

3. **Compare the pH values:**
- HCl will have the lowest pH because it is a strong acid and will produce the highest concentration of H⁺ ions.
- NaHCO₃ and Na₂CO₃ will have higher pH values than HCl since they are weak bases.
- KOH will have the highest pH among all because it is a strong base.

### Conclusion:
The solution with the lowest pH is **HCl**.