What is the pH of 0.1 M HCl?

Answer

To find the pH of a 0.1 M HCl solution, follow these steps:

### Step 1: Understand the nature of HCl
HCl (hydrochloric acid) is a strong acid, which means it dissociates completely in water. This means that all the HCl molecules will break apart into H⁺ ions and Cl⁻ ions.

### Step 2: Write the dissociation equation
The dissociation of HCl in water can be represented as:
\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \]

### Step 3: Determine the concentration of H⁺ ions
Since the concentration of HCl is 0.1 M and it dissociates completely, the concentration of H⁺ ions will also be 0.1 M. Therefore:
\[ [\text{H}^+] = 0.1 \, \text{M} \]

### Step 4: Use the pH formula
The pH of a solution is calculated using the formula:
\[ \text{pH} = -\log[\text{H}^+] \]

### Step 5: Substitute the concentration of H⁺ into the pH formula
Now, substitute the value of [H⁺]:
\[ \text{pH} = -\log(0.1) \]

### Step 6: Calculate the pH
Using logarithmic properties:
\[ \text{pH} = -\log(10^{-1}) = 1 \]

### Final Answer
Thus, the pH of a 0.1 M HCl solution is **1**.

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