1. An unknown solid acid is either citric acid or tartaric acid. To determine which acid you have, you titrate a sample of the solid with NaOH. The appropriate reactions are as follows:
Citric acid:
H3C6H5O7(aq) + 3NaOH(aq) ---> 3H2O(l) + Na3C6H5o7(aq)
Tartaric acid:
H2C4H4O6(AQ) + 2NaOH(aq) ---> 2H2O(l) + Na2C4H4O6(aq)
A 0.956g sample requires 29.1 mL of 0.513 M NaOH for titration to the equivalence point. What is the unknown acid?
2007-09-16 14:37:45 · 1 answers · asked by Vanessa1027 1 in Science & Mathematics ➔ Chemistry
29.1 mL of 0.513 M NaOH is 0.0291*0.513 = 0.014928(Mole).
Since one mole of NaOH reacts with one mole of carboxyl (-COOH) group, this 0.956g sample must contains 0.014928 mole of carboxyl group. The molecular weight of citric acid is 192.027g, and provide 3 carboxyl groups. Hence 0.956g citric acid is: 0.956*3/192.027 = 0.01494 mole of carboxyl group. The molecular weight of tartaric acid is 150.087g, and provide 2 carboxyl groups. Hence 0.956g tartaric acid is: 0.956*2/150.087 = 0.01274 mole of carboxyl group. Therefore, the unknown acid must be citric acid.
2007-09-18 07:44:33 · answer #1 · answered by Hahaha 7 · 0⤊ 0⤋