Measurements show that the pH of a particular lake is 4.0. What is the hydrogen ion concentration of the lake? a. 4.0 M b. 10−10 M c. 10−4 M d. 104 M

Verified step by step guidance

1. Understand the relationship between pH and hydrogen ion concentration. The pH of a solution is defined as the negative logarithm (base 10) of the hydrogen ion concentration: pH = -log[H+].
2. Given that the pH of the lake is 4.0, use the formula to find the hydrogen ion concentration. Substitute the pH value into the formula: [H+] = 10^{-pH}.
3. Calculate the hydrogen ion concentration: [H+] = 10^{-4.0}.
4. Perform the calculation: [H+] = 10^{-4} = 0.0001 M.
5. Match the calculated hydrogen ion concentration with the correct answer choice: c. 10^{-4} M.

Key Concepts

pH Scale

The pH scale measures the acidity or alkalinity of a solution, ranging from 0 to 14. A pH of 7 is neutral, while values below 7 indicate acidity and above 7 indicate alkalinity. Each unit change in pH represents a tenfold change in hydrogen ion concentration, making it a logarithmic scale.

Hydrogen Ion Concentration

Hydrogen ion concentration ([H+]) is a measure of the amount of hydrogen ions present in a solution, typically expressed in moles per liter (M). The relationship between pH and hydrogen ion concentration is given by the formula [H+] = 10^(-pH). Thus, a lower pH corresponds to a higher concentration of hydrogen ions.

Calculating [H+] from pH

To find the hydrogen ion concentration from a given pH, use the formula [H+] = 10^(-pH). For example, if the pH is 4.0, the calculation would be [H+] = 10^(-4.0), resulting in a concentration of 10^(-4) M. This calculation is essential for understanding the acidity of the solution.