CHEM 1212 Midterm-Experiment 8
a)716.9 torr b)16.1% c)0.0031 moles d)0.93 M
2. What is the partial pressure of O2 if the barometric pressure is 745.2 torr and the water temperature was 28°C? b. 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. c. 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? d. What is the Molarity of an H2O2 solution if 0.00362 moles of O2 was produced by 7.82 mL of H2O2 solution?
89.8 mL of O₂
How many mL of O2 would be produced by the reaction of 8.03 mL of 30.0% H2O2? The barometric pressure (Patm) was 752.4 torr and the temperature was 24.0°C. (Hint: Work this problem in reverse. Convert % H2O2 by mass to M of H2O2, then moles of H2O2, then moles of O2, then L of O2.)
a)the O₂ level would decrease as air escaped and our calculations for molarity of H₂O₂ would be lower than true value. b) This would cause you to calculate a lower value for the moles of O₂ which would lead to a lower Molarity of H₂O₂.
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.
P(atm) = P(H₂O) +P(O₂) PO2=Patm-PH2O
Patm formula Manipulate to find PO2
His will be lower because when calculating moles of O₂, you are multiplying by a lower volume, which would produce fewer moles of O₂ produced. This would cause him to calculate fewer moles of H₂O₂ and a lower molarity of H₂O₂. A lower molarity of H₂O₂ would produce a smaller % of H₂O₂by mass.
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.
Pv=nRT
Pv=???
To catalyze the decomposition of the hydrogen peroxide
What is the purpose of the yeast in this experiment?
To find the partial pressure of O2
Why do we need to subtract the water vapor pressure from the barometric pressure?
