Question

Two students titrated a 25.0 mL aliquot of pear juice with 0.107 M NaOH to the phenolphthalein end point. The initial buret reading was 0.73 mL and the final buret reading was 18.39 mL. a. What is the mass of citric acid in the juice sample?

Answer 1

Answer:

0.363g citric acid

Explanation:

Sodium hydroxide (NaOH) reacts with acids, thus:

NaOH + H⁺ → H₂O + Na⁺

The volume of titration is:

18.39mL - 0.73mL = 17.66mL

Moles of this volume in 0.107M NaOH are:

0.01766L × (0.107 mol / L) = 0.00189mol NaOH ≡ mol citric acid -Assuming the only acid in pear juice is citric acid-

As molar mass of citric acid is 192.124g/mol:, Mass of citric acid is:

0.00189mol citric acid × (192.124g / mol) = 0.363g citric acid

I hope it helps!