Challenge Problem: CHEMISTRY
2009-05-18 3:56 pm
A researcher has an unknown biological compound that she knows is a diprotic acid. She weighs out 1.297 grams of the unknown acid, dissolves it in water, adds an indicator, and titrates it to neutrality using 73.85 mL of 0.1569 M NaOH. What is the molecular weight of the acid?
回答 (1)
2009-05-18 6:34 pm
✔ 最佳答案
Denote the dibasic acid as H2A.
Consider the titration:
H2A + 2NaOH → Na2A + 2H2O
Mole ratio H2A : NaOH = 1 : 2
No. of moles of NaOH used = 0.1569 x (73.85/1000) = 0.011587 mol
No. of moles of H2A used = 0.011587 x (1/2) = 0.005794 mol
Molar mass of H2A= 1.297/0.005794 = 223.9 g/mol
Molecular weight of the acid = 223.9
=
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