Question

A titration is a procedure for determining the concentration of a solution by allowing it to react with another solution of known concentration (called a standard solution). Acid-base reactions and oxidation-reduction reactions are used in titrations. For example, to find the concentration of an HCl solution (an acid), a standard solution of NaOH (a base) is added to a measured volume of HCl from a calibrated tube called a buret. An indicator is also present and it will change color when all the acid has reacted. Using the concentration of the standard solution and the volume dispensed, we can calculate molarity of the HCl solution.

Part A

A volume of 70.0 mL of aqueous potassium hydroxide (KOH) was titrated against a standard solution of sulfuric acid (H2SO4). What was the molarity of the KOH solution if 17.7 mL of 1.50 M H2SO4 was needed? The equation is

2KOH(aq)+H2SO4(aq)→K2SO4(aq)+2H2O(l)

Express your answer with the appropriate units.

Redox titrations are used to determine the amounts of oxidizing and reducing agents in solution. For example, a solution of hydrogen peroxide, H2O2, can be titrated against a solution of potassium permanganate, KMnO4. The following equation represents the reaction:

2KMnO4(aq)+H2O2(aq)+3H2SO4(aq)→3O2(g)+2MnSO4(aq)+K2SO4(aq)+4H2O(l)

A certain amount of hydrogen peroxide was dissolved in 100. mL of water and then titrated with 1.68 M KMnO4. What mass of H2O2 was dissolved if the titration required 18.3 mL of the KMnO4 solution?

Express your answer with the appropriate units.

Answer 1

2KOH(aq) +   H2SO4(aq)→K2SO4(aq)+2H2O(l)

2 moles        1 moles

KOH                                                                     H2SO4

M1 =                                                                 M2 = 1.5M

V1 = 70ml                                                         V2 = 17.7ml

n1 = 2                                                                 n2 = 1

                  M1V1/n1     =     M2V2/n2

                         M1       = M2V2n1/n2V1

                                    = 1.5*17.7*2/1*70

                                    = 0.756M

B.

2KMnO4(aq)+H2O2(aq)+3H2SO4(aq)→3O2(g)+2MnSO4(aq)+K2SO4(aq)+4H2O(l)

2 moles          1mole

no of moles of KMnO4 = molarity * volume in L

                                      = 1.68*0.0183   = 0.03074moles

from balanced equation

2moles of KMnO4 react with 1 mole of H2O2

0.03074 moles of KMnO4 react with =1*0.03074/2 = 0.0154moles of H2O2

mass of H2O2 = no of moles * gram molar mass

                         = 0.0154*34 = 0.5236g >>> answer