A solution of HCl has [tex]$\left[ H^{+}\right] = 0.01 \, M$[/tex]. What is the pH of this solution? Use [tex]$pH = -\log \left[ H _3 O ^{+}\right]$[/tex].

A. -2
B. -1
C. 1
D. 2



Answer :

To determine the pH of the solution, let's follow a step-by-step process:

1. Identify the given hydrogen ion concentration:
[tex]\[ \left[ H^+ \right] = 0.01 \, \text{M} \][/tex]

2. State the formula for pH:
[tex]\[ \text{pH} = -\log \left[ H_3O^+ \right] \][/tex]
Note that [tex]\( \left[ H_3O^+ \right] \)[/tex] and [tex]\( \left[ H^+ \right] \)[/tex] are used interchangeably here because they represent the concentration of hydrogen ions in the solution.

3. Substitute the given hydrogen ion concentration into the formula:
[tex]\[ \text{pH} = -\log \left( 0.01 \right) \][/tex]

4. Recall the property of logarithms:
[tex]\[ \log(b^n) = n \cdot \log(b) \][/tex]
Since [tex]\( \log(10) = 1 \)[/tex], we can use this property on [tex]\( 0.01 \)[/tex]:

5. Express [tex]\( 0.01 \)[/tex] as a power of 10:
[tex]\[ 0.01 = 10^{-2} \][/tex]

6. Apply the logarithm rule:
[tex]\[ \log(10^{-2}) = -2 \cdot \log(10) = -2 \cdot 1 = -2 \][/tex]

7. Substitute the log value into the pH formula:
[tex]\[ \text{pH} = -(-2) \][/tex]
[tex]\[ \text{pH} = 2 \][/tex]

Therefore, the pH of the solution is:

[tex]\[ \boxed{2} \][/tex]