Question:
What is the pH of 1 molar HCl solution? (assume complete dissociation)
What is the pH of 1 molar HCl solution? (assume complete dissociation)
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Strong acid gives [H+] equal to its molarity; take the negative log.
Updated On: Oct 1, 2026
- \(1\)
- \(2\)
- Zero
- \(7\)
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept
HCl is a strong acid. The question tells us to assume complete dissociation, so each mole of HCl gives one mole of \(\text{H}^+\).
Step 2: Key Formula or Approach
\[ \text{pH}=-\log[\text{H}^+] \]
Step 3: Hydrogen ion concentration
\[ \text{HCl}\to\text{H}^++\text{Cl}^-,\qquad [\text{H}^+]=1\ \text{M} \]
Step 4: Calculation
\[ \text{pH}=-\log(1)=0 \]
Step 5: Why the other options are wrong
A pH of 1 needs 0.1 M acid and a pH of 2 needs 0.01 M acid. A pH of 7 belongs to pure water. Because 1 M is the unit concentration, the logarithm is zero. A pH of zero is perfectly allowed, since the pH scale is not limited to values between 0 and 14 in strong solutions.
Final Answer:
The pH of 1 M HCl is 0, option (C). \[ \boxed{0} \]
HCl is a strong acid. The question tells us to assume complete dissociation, so each mole of HCl gives one mole of \(\text{H}^+\).
Step 2: Key Formula or Approach
\[ \text{pH}=-\log[\text{H}^+] \]
Step 3: Hydrogen ion concentration
\[ \text{HCl}\to\text{H}^++\text{Cl}^-,\qquad [\text{H}^+]=1\ \text{M} \]
Step 4: Calculation
\[ \text{pH}=-\log(1)=0 \]
Step 5: Why the other options are wrong
A pH of 1 needs 0.1 M acid and a pH of 2 needs 0.01 M acid. A pH of 7 belongs to pure water. Because 1 M is the unit concentration, the logarithm is zero. A pH of zero is perfectly allowed, since the pH scale is not limited to values between 0 and 14 in strong solutions.
Final Answer:
The pH of 1 M HCl is 0, option (C). \[ \boxed{0} \]
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