A dilute solution of an unknown weak acid required a 28.62 mL titration with 0.1084 M NaOH to reach a phenolphthalein end point. Calculate the equivalent mass of the acid if the sodium salt was found to weigh 0.2110 g.

Question

jfraser · Answer

all neutralization reactions have the same general formula:$$H-A + M-OH \rightarrow H_2O + MA$$ where $H-A$ is the generalized form of any acid and $M-OH$ is a metal hydroxide (the base). Even if the actual reaction isn't a 1:1 mole ratio, we can assume it is in order to find the equivalent mass of the unknown acid.

Knowing the volume and concentration of the base used lets you find the $moles$ of base that were used in the neutralization.

The $moles$ of base used will equal the $moles$ of acid used, because of the molar ratio.

The $equivalent \space mass$ of the acid will be the moles neutralized divided by the $mass$ of acid neutralized.