According to the balanced equation below, how many moles of #ClO^-2 (aq)# are needed to react completely with 20. mL of 0.20 M #KMnO_4# solution?

#2H_2O(l) + 4MnO_4(aq) + 3ClO_2^(-)(aq) -> 4MnO_2(s) + 3ClO_4^(-)(aq) + 4OH^(-)(aq)#

1 Answer
Dec 18, 2016

Answer:

#3*mmol# #"chlorite anion"# are required.

Explanation:

#"Reduction"#
#MnO_4^(-) +4H^(+) + 3e^(-) rarr MnO_2(s) + 2H_2O(l)# #(i)#

#"Oxidation"#
#ClO_2^(-) +2H_2O rarr ClO_4^(-) + 4H^+ +4e^-# #(ii)#

#"Overall"# #4xx(i) +3xx(ii)#
#4MnO_4^(-) +3ClO_2^(-) +4H^+rarr 4MnO_2(s) +3ClO_4^(-)+ 2H_2O(l)#

#"Moles of "KMnO_4=20xx10^-3Lxx0.20*mol*L^-1=4.0xx10^-3*mol#

Given the equation, we need 3/4 equiv of chlorite anion,

#3/4xx4.0xx10^-3*mol#

What would you observe in this reaction? What was the macroscopic colour change?