F4 chem (urgent)
2009-04-26 7:47 am
Orange juice contains citric acid. The relative molecular mass of citric acid is 192. In a sample of orange juice, the concetration of citric acid is 9.06 g dm^-3. 25.00 cm^3 of the sample require 7.50 cm^3 of 0.42M sodium hydroxide solution for complete neutralization. Determine the basicity of citric acid.
回答 (1)
2009-04-27 2:35 am
✔ 最佳答案
Let n be the basicity of citric acid,
and denote citric acid as HnX.
HnX + nNaOH → NanX + nH2O
Mole ratio HnX : NaOH = 1 : n
Molarity of HnX = 9.06/192 = 0.0472 M
No. of moles of HnX used = 0.0472 x (25/1000) = 0.00118 mol
No. of moles of NaOH = 0.42 x 7.5/1000 = 0.00315
Basicity, n = 0.00315/0.00118 ≈ 3
=
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