To find the citric acid concentration in lemon juice with a pH of 2, we can use the relationship between pH and hydrogen ion concentration. The pH scale measures how acidic or basic a solution is, with lower values indicating higher acidity.
Understanding pH and Hydrogen Ion Concentration
The formula to convert pH to hydrogen ion concentration \([H^+]\) is:
- \([H^+] = 10^{-\text{pH}}\)
For a pH of 2:
- \([H^+] = 10^{-2} = 0.01 \, \text{M}\)
Citric Acid Dissociation
Citric acid (\(C_6H_8O_7\)) is a triprotic acid, meaning it can donate three protons (hydrogens). However, since we are only considering the first hydrogen, we can simplify our calculations. The dissociation of citric acid can be represented as:
- \(C_6H_8O_7 \rightleftharpoons H^+ + C_6H_7O_7^-\)
In this case, the concentration of hydrogen ions \([H^+]\) is equal to the concentration of the first dissociated form of citric acid.
Calculating Citric Acid Concentration
Since all the hydrogen ions come from citric acid, the concentration of citric acid can be approximated to be equal to the concentration of hydrogen ions:
- Citric acid concentration \(\approx 0.01 \, \text{M}\)
Therefore, the citric acid concentration in the lemon juice is approximately 0.01 M.
