Q.
10mL of NaHC2O4 solution is neutralized by 10mL of 0.1MNaOH solution. 10mL of same NaHC2O4 solution is oxidized by 10mL of KMnO4 solution in acidic medium. Hence, molarity of KMnO4 is
215
190
Some Basic Concepts of Chemistry
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Solution:
NaHC2O4⇌Na++H++C2O42− H+≡OH−
and C2O42−≡MnO4− H++OH−→H2O C2O42−→2CO2+2e− MnO4−+8H++5e−→Mn2+ 10mL of NaHC2O4≡10mL of 0.1MNaOH
Thus, 10×M(NaHC2O4)=10×0.1 M=0.1M=0.1N ( since H+is neutralized) NaHC2O4=0.1N as an acid =0.2N as C2O42− oxidised by MnO4−
Let MnO4−=xM=5xN 10mL of 0.2NNaHC2O4≡10mL of 5×NMnO4 10×0.2=10×5x ∴x=50.2=0.04M