Considering a 0.1 M formic acid buffer, what is the concentration of formic acid present in a solution of pH 4.25 if the pK of formic acid is 3.75?

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The Henderson-Hasselbalch equation can be used to calculate the concentration of formic acid present in a solution of pH 4.25:```pH = pK + log([A-]/[HA])```where:* pH is the pH of the solution* pK is the dissociation constant of the acid* [A-] is the concentration of the conjugate base* [HA] is the concentration of the acidIn this case, the pH is 4.25, the pK is 3.75, and the concentration of the conjugate base is 0.1 M. Substituting these values into the equation, we get:```4.25 = 3.75 + log([A-]/0.1)```Solving for [A-], we get:```[A-] = 0.024 M```Therefore, the concentration of formic acid present in the solution is:```[HA] = 0.1 M - [A-] = 0.1 M - 0.024 M = 0.076 M```