A scond standardized solution of 0.0214 M KMno, s used to analyze an opened bott

Question

A scond standardized solution of 0.0214 M KMno, s used to analyze an opened bottle H20, solution to determine th e % by mass of H202. The net ionic equation for this reaction is so 6 H'( aq)+ 2 MnO(a)+ 5H,O,(ag)-2 Mn2"(ag)+502(g)+8H2O(ag A 300 mL sample H202 titraed to the endpoint with the KMnO, delivered from the buret. The volume of 0.0 reqired to reach the endpoint is 34.70 mL. Assume the density of the H,0, solution is e of the HO2 solution is placed in a flask, acidifed with 2 mL of 6M H,SO4, and he volume of 0.0214 M KMnO 1.00g/ mL Volume of ? % H2O2 Volume of 0.0214 M KMnO 3470 mL mass of the H2O2 solution. Assume the density of the H2O2 solution is 100g/ 3.00 mL (e) Calculate the % by mL. f) If the endpoint of the titration reaction is overshot, will the student's calculated value for the % (g) i. Define the following terms H,O2 increase, decrease, or remain the same? Explain. Analyte: Titrant: ii. In this lab, there was a substance that served as both a titrant and an analyte. Identify the substance and explain how it acted as both.

Explanation / Answer

Titration of H2O2 by KMnO4:

mol of titrant KMnO4 used up=molarity*volume=0.0214mol/L*0.03470L=0.000743 mol

from the balanced redox reaction equation it follows that :

mol of KMnO4 used/mol of H2O2=2/5

Thus, mol of H2O2 reacted=5/2 (mol of KMnO4)=5/2*0.000742mol=0.00186 mol

Thus mass of H2O2 reacted=mol *molar mass of H2O2=0.00186 mol*(34.015g/mol)=0.0633g

Now total mass in 3.0 ml H2O2=density*volume=(1.0g/ml)*(3.0ml)=3.0g

Actual mass of H2O2 present =0.0633g

e) % mass of H2O2 =(actual mass/total mass)*100=(0.0633/3.0)*100=2.11%

f) If end point of the titration is over shot ,you get higher value of volume of titrant ,thus you get higher value of mol of KMnO4 which leads to higher value of mol/mass of H2O2 in the solution ,and thus a higher % by mass of H2O2.

g)i) Analyte =unknown sample for which concentration is to be determined.(H2O2)

titrant =standardized reactant of known concentration added to the analyte dropwise to calculate the endpoint of reaction with theanalyte Here.(KMnO4) is the titrant (added from burette)

ii)H2SO4 or acid is added to both titrant and the analyte

Analyte =3.0 ml H2O2+2ml 6M H2SO4

titrant =acidified KMnO4

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