1. Dalton’s Law of Partial Pressures/Effusion 1.Calculate and use the pressure in torr. 2.Determine the partial pressure of the light molecules. 3.Determine the partial pressure of the light molecules. 4.Calculate the partial pressure of the heavy molecules.

2. Dalton’s Law of Partial Pressures/Effusion A chemist collects H 2 over H 2 O using the diagram shown right. The pressure (total) In the bottle is 745 mmHg, T = 30 o C, and the total volume (H 2 & H 2 O) is 371 mL. See also Tro Figure 5.14 page 201. 1. Write the partial pressure (vapor pressure) of H 2 O at 30 o C. ANS: Vap. Press. = 32 torr (mmHg) 2. Calculate the moles of H 2 O. ANS = 6.28 X 10 -4 mol 3. Calculate the partial pressure of H 2. ANS = 713 torr 4. Calculate the moles of H 2. ANS = 0.0141 mol 5. Which molecule has the greatest velocity? Show effusion from slide 1.

3. Dalton’s Law of Partial Pressures A chemist collects O 2 over H 2 O. P total = 0.952 atm, T = 35 o C, and V total = 521 mL. The vapor pressure of water at 35 o C is 42 torr. [Tro page 201 - table 5.4]. 1.Calculate the vapor pressure of water in atm. ANS: 0.055 atm 2. Calculate the partial pressure of O 2. ANS: 0.897 atm 3. Calculate the moles of O 2. ANS: 0.0185 mol

4. Dalton’s Law of Partial Pressures A chemist has a gas sample (P total = 1.24 atm) consisting of 0.61 mol of He and 2.77 mol of Ne. Calculate the partial pressures of He and Ne. ANS: P He = 0.22 atm P Ne = 1.02 atm