CHEM 1212: Exp. 8- Determining % Composition of Hydrogen Peroxide

Which statements explain the shape of the titration curve observed in lab?

- During the reaction, the conductivity decreases due to the production of nonelectrolytes. - After the endpoint, the conductivity increases due to the excess titrant.

Purpose of experiment 8

Determine the % mass composition of H2O2 by measuring the production of O2

Perry read the final volume of gas as 88.6 mL before aligning the water levels. His partner Ida read the final volume of gas as 91.3 mL AFTER aligning water levels. Will Perry's calculation of percent by mass be higher or lower than Ida's? Explain your reasoning.

His calculation will be lower because the final gas will be calculated to find mols of O2 which will be lower than the true value, and will cause molarity of H2O2 to be lower, and ultimately the percent by mass calculation lower as well

What is the partial pressure of O2 if the barometric pressure is 745.2 torr and the water temperature was 28°C? a) What is the % by mass composition of H2O2 if the Molarity of the H2O2 is 4.72 M? Assume the density of the H2O2 is 1.00 g/mL. b) How many moles of O2 are present if 79.3 mL of O2 has a partial pressure of 721.8 torr at 23.7°C? c) What is the Molarity of an H2O2 solution if 0.00362 moles of O2 was produced by 7.82 mL of H2O2 solution?

Partial pressure= 716.9 torr a) 16.05% b) 0.00309 mols O2 c) 0.92583 M

Why do we need to subtract the water vapor pressure from the barometric pressure?

To find the partial pressure of O2

How would the following errors affect the calculation of Molarity of H2O2? Explain your answers. a) The rubber stopper with the attached hose was not fitted tightly into the test tube after the yeast was added. (Some gas escaped out of the test tube.) b) The initial volume of gas in the graduated cylinder was recorded as zero instead of 3.5 mL.

a) Since some gas escaped out the tube the value would decrease, decreasing the molarity of H2O2 b) This would cause a lower value for the mols of gas which would decrease the molarity of H2O2

In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) •BaSO4

non electrolyte

In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) •Ba(OH)2

strong electrolyte

What is the purpose of the yeast in this experiment?

to catalyze the decomposition of H2O2