A titration is a procedure for determining the concentration of a solution by al

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 HC1 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 40.0 mL of aqueous potassium hydroxide (KOH) was titrated against a standard solution of sulfuric acid (H_2SO_4). What was the molarity of the KOH solution if 14.2 mL of 1.50 M H_2SO_4 was needed? The equation is 2KOH(aq) + H_2SO_4(aq) rightarrow K_2SO_4(aq) + 2H_2O(l) Express your answer with the appropriate units. molarity = 1.07 M Correct The solution in the buret (in this case, H_2SO_4) is called the titrant. The sample in the flask (in this case, KOH) is called the analyte. The stage in a titration when the exact volume of solution needed to complete the reaction has been added is called the stoichiometric point or equivalence point. To detect the equivalence point, a few drops of an acid-base indicator are added to the analyte before the titration. Part B Redox titrations are used to determine the amounts of oxidizing and reducing agents in solution. For example, a solution of hydrogen peroxide, H_2O_2, can be titrated against a solution of potassium permanganate, KMnO_4. The following equation represents the reaction: 2KMnO_4 (aq) + H_2O_2(aq) + 3H_2SO_4(aq) rightarrow 3O_2(g) + 2MnSO_4(aq) + K_2SO_4 (aq) + 4H_2O(l) A certain amount of hydrogen peroxide was dissolved in 100. mL of water and then titrated with 1.68 M KMnO_4. What mass of H_2O_2 was dissolved if the titration required 13.8 mL of the KMnO_4 solution? Express your answer with the appropriate units. mass of H_2O_2 =

Explanation / Answer

firsty, find mol of KMNO4

mol = MV = 13.8 *10^-3 *1.68 = 23.184*10^-3 mol of KMnO4

so..

from the equation

2 mol of KMnO4 --> 1 mol o fH2O2

23.184*10^-3 mol of KMnO2 --> 1/2*23.184*10^-3 = 11.592*10^-3 mol of H2O2

mass H2O2 = mol*MW = (11.592*10^-3)(34) = 0.3941 g of H2O2

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