homework 10 - 1. Analysis of a sample of a gaseous compound...

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1. Analysis of a sample of a gaseous compound shows that it contains 85.6% C and 14.4% H by mass. At standard conditions (STP), 148.8 mL of the compound weighs 0.186 g. What is the molecular formula of the compound? 2. A volatile liquid was put into a flask with a volume of 150.5 mL, then the flask was put into a boiling water bath. The temperature of the water was measured at 99.9 o C, and the atmospheric pressure was 760.0 torr. The flask was removed, was quickly cooled to condense the volatile liquid, dried and weighed. The mass of the flask and the volatile liquid is 34.730 grams. If the mass of the flask without the volatile liquid is 34.133 grams, determine the molar mass of the liquid. 3. In the previous question where one determined the molar mass of a liquid, it was important that the flask was cooled before weighing the flask containing the condensed liquid. Why was it important that the flask was cooled? 4. What is the density of nitrogen dioxide gas at 738.8 torr and 29.5 °C? 5. A sample of dry air of total mass 1.000 g consists of 0.760 g of nitrogen and 0.240 g of oxygen. Calculate the partial pressures of these gases and the total pressure (in atm) when this sample is in a flask of 1.22 L at 21.1 °C. a. The partial pressure of nitrogen gas is ___atm b. The partial pressure of oxygen gas is ___atm c. The total pressure in the flask is ___atm 6 The above sample is heated until the total pressure is 1.85 atm. What are the partial pressures of nitrogen and oxygen in the heated sample? (You will need to calculate the mole fractions of each gases first. See pages 449 - 451 of your textbook.) a. nitrogen ___atm b. oxygen ___atm 6. Two tanks are connected by a closed valve. Tank A contains 5.06 L of O 2 at 20.1 atm and tank B contains 2.56 L of N 2 at 35.9 atm. What is the pressure inside the tanks after the valve is opened? Assume ideal gas behavior for both gases. _____atm a. What is the mole fraction of O 2 ? b. What is the mole fraction of N 2 ? 7. A 5.50 g sample containing solid potassium chlorate and other inert impurities was heated in a test tube. The potassium chlorate in the sample completely decomposed into potassium chloride and oxygen gas. The oxygen produced was collected over water (similar to Figure 12-7 on page
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homework 10 - 1. Analysis of a sample of a gaseous compound...

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