Logarithms
pH
Examples
Example 1 Find the pH of apple juice with a hydrogen ion concentration of 3.2 x 10-4 .Step 1. Substitute 3.2 x 10-4 in the formula.
![pHEx1-1 pHEx1-1](https://claregladwinresd.glk12.org/pluginfile.php/960/mod_book/chapter/396/Exponential_and_Logarithmic_Functions/Images/pHEx1-1.png)
Step 2. Use a calculator to solve.
![pHEx1-2 pHEx1-2](https://claregladwinresd.glk12.org/pluginfile.php/960/mod_book/chapter/396/Exponential_and_Logarithmic_Functions/Images/pHEx1-2.png)
Example 2 Find the hydrogen ion concentration of ketchup which has a pH of 3.9.
Step 1. Substitute 3.9 into the formula.
![pHEx2-1 pHEx2-1](https://claregladwinresd.glk12.org/pluginfile.php/960/mod_book/chapter/396/Exponential_and_Logarithmic_Functions/Images/pHEx2-1.png)
Step 2. Use the inverse operations of logs and exponents and a calculator to solve.
![pHEx2-2 pHEx2-2](https://claregladwinresd.glk12.org/pluginfile.php/960/mod_book/chapter/396/Exponential_and_Logarithmic_Functions/Images/pHEx2-2.png)
![pHEx2-3 pHEx2-3](https://claregladwinresd.glk12.org/pluginfile.php/960/mod_book/chapter/396/Exponential_and_Logarithmic_Functions/Images/pHEx2-3.png)
![pHEx2-4 pHEx2-4](https://claregladwinresd.glk12.org/pluginfile.php/960/mod_book/chapter/396/Exponential_and_Logarithmic_Functions/Images/pHEx2-4.png)