pH value of 0.1 N HCl solution is approximately:

Question

pH value of 0.1 N HCl solution is approximately:

1. A. 1.0 (Correct answer)
2. B. 11.0
3. C. 10
4. D. 2.0

Correct Answer

Option A — 1.0

Detailed Solution & Explanation

The correct answer is 1.0.

Key Points

• Hydrochloric acid (HCl) is a strong acid and a monobasic (monoprotic) acid, meaning it dissociates completely in water and each molecule releases exactly one hydrogen ion.
• For a monobasic acid, normality equals molarity, so a 0.1 N HCl solution is also 0.1 M, giving a hydrogen ion concentration of [H⁺] = 0.1 = 10⁻¹ mol/L.
• Applying the definition of pH:
• pH = −log₁₀[H⁺] = −log₁₀(10⁻¹) = 1.0
• The pH scale runs from 0 to 14 at 25 degrees Celsius: values below 7 are acidic, 7 is neutral and above 7 are basic.
• The scale is logarithmic, so a change of one pH unit means a tenfold change in hydrogen ion concentration.

Exam Tip

• for a strong monobasic acid, the shortcut is simply pH = −log(concentration) — so 0.01 M HCl has pH 2 and 0.001 M HCl has pH 3.
• Note that this shortcut fails for weak acids such as acetic acid, which dissociate only partially.

प्रश्न (हिन्दी में)

0.1 एन HCl समाधान का पीएच मान है लगभग:

1. A. 1.0
2. B. 11.0
3. C. 10
4. D. 2.0