Question

How do you determine the pH of citric acid?

Answer 1

Citric Acid:

1. It is an organic compound of chemical formula${\mathrm{C}}_6{\mathrm{H}}_8{\mathrm{O}}_7$.
2. It is found in citrus fruits.
3. Because citric acid is a solid substance, its pH cannot be determined.
4. The aqueous solution of citric acid is used to determine its pH.

Example:

1. If we have to calculate the pH of $0.002\mathrm{M}$ citric acid solution we will use the pH formula $=-{\log }_{10}\left[{\mathrm{H}}^{+}\right]$ where [${\mathrm{H}}^{+}$] is the molar concentration of H⁺ ion.
2. $\mathrm{pH}=-\log \left[{\mathrm{H}}^{+}\right]\Rightarrow -\log \left[0.002\right]\Rightarrow 2.69$
3. $\mathrm{pH}=2.69$

Therefore, the pH of citric acid is around $2-3$ which means it is a strong acid among all organic acids.