Physical Chemistry for Biologists Test 1 PDF

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Mid-term exam for CHE 341 was given during the special semester of 2021 at Cuttington University in Liberia. The topics covered are basic laws of gases and applications...

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Cuttington University Suakoko, Bong County, Liberia Chem 341 Test 1 Name: __________________________________ I. D. #: _________________ Score: ______% Date: May 13, 2021 Part 1: Answer the following questions [40 pts]. 1. What is the density (in g/L) of a gas with a molar mass of 60 g/mol at 0.75 atm and 27 °C? 2. Find the volume of 0.5mol of CH4 under 3.28 atm pressure and 400 K temperature. [ Hint: Use R = 0.0821 atm*L/(mol*K) if necessary]. 3. A gas sample occupies 350 mL at 546 mm Hg. What volume does the gas occupy at 652 mm Hg? Which gas law is used for this problem? 4. A birthday party balloon is filled with 0.045 grams of Helium gas. If the balloon takes up 750 mL of space and has a pressure of 325 mm Hg, what is the temperature inside the balloon? [Hint: The molar mass of Helium is 4.0026 g/mole and R = 62.4 L*mmHg/(mol*K) 5. A container holds a mixture of nitrogen (N2), argon (Ar) and methane (CH4) gases. The partial pressures are 500 torr for nitrogen, 300 torr for argon and 200 torr for methane. What is the mole fraction for methane? Part 2: Circle the letter bearing the correct answer. Do not erase [30 pts]. 1. According to Charles Law, if you have a balloon inside a car at noon during a hot summer day the balloon molecules inside will increase in pressure. A. True B. False C. Neither ‘A’ nor ‘B’ D. Either ‘A’ or ‘B’ 2. If nitrogen gas occupies has a volume of 500 ml at a pressure of 0.971 atm. What volume will the gas occupy at a pressure of 1.50 atm., assuming the temperature remains constant? A. 342mL B. 424mL C. 324mL D. 442mL E. 242mL 3. According to Boyle’s Law, as the volume of a confined gas decreases at constant temperature, the pressure exerted by the gas ______. A. Decreases B. Increases C. Remains the same D. Fluctuates

4. Assuming that the temperature of a gas remains constant, how can you increase the pressure of the gas? A. Increase the container volume B. Add more molecules of the gas C. Decreases the container volume D. None of the above 5. If V, P, and T represent the original volume, pressure, and temperature in the correct units, and V', P', and T' represent the new conditions, what is the combined gas law? A. B. C.

D.

6. Gas A and gas B (both unreactive) are allowed to mix. The total pressure is found to be 3.50 atm. If gas B was measured initially at 1.25 atm, what is the partial pressure of gas A? A. 4.75 atm B. -2.25 atm C. 2.25 atm D. 1.25 atm

PART III: For each expression in the first column, write the letter of the expression in the second column that is most closely related [ 30 pts] Colume A a. Dalton’s law b. Charles’s law c. Gay-Lussac’s law d. Boyle’s law

e. combined gas law f. Pascal’s law g. gas pressure law h. ideal gas law i. Gay-Lussac’s law of combining volumes j. Avogadro’s law k Graham’s law l. No basis for answering

Column B 1._____The pressure of a fixed mass of gas varies directly with the Kelvin temperature at constant volume 2. ____The pressure of a fixed mass of gas varies directly with the Kelvin temperature at constant volume 3.____The volume of a fixed mass of gas varies inversely with the pressure at constant temperature. 4.____At constant temperature and pressure, the volumes of gaseous reactants and products can be expressed as ratios of small whole numbers. 5.____Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. 6._____The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases. 7.____The relationship between pressure, volume, and temperature is expressed by this law 8.____Pressure times volume equals molar amount times 0.0821 L atm/(mol K) times temperature in kelvins. 9.____ The rates of effusion of gases at the same temperature and pressure are inversely proportional to their molar masses. 10.___ The volume of a fixed mass of gas varies directly with the Kelvin temperature at constant pressure....