a) Write balanced half equations for the redox reaction of Cr^ n+
and MnO4- in acidic solution .In terms of n, how many moles of
electrons per mole of Cr^ n+ , are involved in the oxidation reaction ?
Write the balanced overall chemical equation for the above reaction .
b)An acidified solution containing 1.5x10 ^-3 mol of Cr^n+ is titrated with 0.0250 M KMnO4 solution .The equivalence point of the reaction is reached after 48 cm^3 of KMnO4 has been added.
Calculate the value of n.
Titration
2009-02-22 8:02 am
回答 (1)
2009-02-22 9:00 am
✔ 最佳答案
a)Half equations:
2Crn+ + 7H2O → Cr2O72- + 14H+ + (12 - 2n)e-
MnO4- + 8H+ + 5e- → Mn2+ + 4H2OH
No. of moles of electrons per mol of Crn+
= (12 - 2n)/2
= (6 - 2n) mol
Overall equation:
10Crn+ + (12-2n)MnO4- + (8n-13)H2O→ 5Cr2O72- + (12-2n)Mn2+ + (16n-26)H+
OR:
10Crn+ + (12-2n)MnO4- + (26-16n)H+ → 5Cr2O72- + (12-2n)Mn2+ + (13-8n)H2O
b)
Mole ratio Crn+ : MnO4-
(1.5 x 10-3) : (0.025 x 48/1000) = 10 : (12 - 2n)
(1.5 x 10-3) : (1.2 x 10-3) = 10 : (12 - 2n)
5 : 4 = 5 : (6 - n)
6 - n = 4
n = 2
=
收錄日期: 2021-04-29 18:16:38
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