Question

From the amount of titrant needed to reach the end point and the volume of the aliquot of citric acid solution used, the the facto label method and determine the moles of acidic hydrogen atoms in each flask. How do i determine number of acidic hydrogen atoms in a flask, as in how do i go about? How should i start and what should i end up with?

Answer 1

METHOD

take 25mL of an aliquot of citric acid in a conical flask.

fill the burette with NaOH of concentration N1 ( abase require to titrate the citric acid)

add 5-6 drops of phenolphthalein into the conical flask containing the citric acid.

place the conical below the burette and start titrating drop by drop. you will see the appearance and disappearance of pink colour.

the point where the entire solution turns pale pink will be the endpoint.

note down the volume of NaOH used. ( V1)

CALCULATIONS

1) CONCENTRATION OF CITRIC ACID :

the molar concentration of citric acid 3 volume of acid ( 25.0mL) = Molar concentration of NaOH volume of NaOH (mL)

the concentration of citric acid = (N1 V1 ) / ( 75.0)

2) moles of H+

Moles of H+ = ( the concentration of citric acid obtained 25.0mL) / 1000mL

3) Number of H+

number of H+= moles of H+ Avogadro number