ch1020_2008b_exam1solns

ch1020_2008b_exam1solns - MacDonald. CHMIUZO. I ll] 1/2008....

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Unformatted text preview: MacDonald. CHMIUZO. I ll] 1/2008. Exam I Name: {a /U 7‘! ‘0“ 5 Score: —— I75 You must show your work in order to receive partial credit on problems. Potentially useful information R = 0.08206 L0atm/mol-K STP = 0 °C and l .00 mm 0 °C = 273 K 1 atm = 760 torr = 760 mm Hg 1 mol of gas at STP occupies 22.4 L I. If you place |2.5 g of liquid nitrogen (N,) into an empty balloon and seal it. what will be the volume of the balloon at STP (standard temperature and pressure) after all the liquid nitrogen converts to N3 gas? [5 ptsl [M0] N1) _ A} an7fia ._ o. 946 Mal .1 1.1.5). All 317* the M < #pJ 2.2.4.1.. 0.446454“); Mp! ML) = Z)jL “A have“: '35 < X L d" ( 373x ) ,4 KT ‘_ 0.4% Mb] magma—LT”! 021-3732; Vl- p - [sic-1 w = L M2. 2. Backpacking stoves commonly use canisters of fuel that contain mixtures ol'contpressed propane (Cilia) gas and butane (CJ I...) gas. When a stove is turned on. the mixture of gases is released from a pinhole and then ignited. a. Calculate the relative rate at which propane effuses compared to butane. [4 ptsl A443,!r oj/MOI ’0 Q’Q‘bicr F455£¢F M441 6,, My “4024 I M . . “((45 54.54:: 69“ :vaI7 Cat/r Iva-x /¢:rx Me-a’! h. Does propane diffuse faster. slower. or at the saute rate as butane? Circle your answer. [2 ptsl slower at the same rate .\ a. Carbon dioxide gas (C03) commonly is used in fire extinguishers because it is heavier than air and retards combustion by displacing oxygen. Calculate the density (d) ol‘CO; iIt g/L at 22.0 °C at 755 torr. [5 pts] d _ M.» f (44.05/ml) (755‘ fi»)!%) 40‘. ~ % — = R ‘ (gonzo; :z,x)@2_o;*2732) A/IUCIMMUM, C HAW/020. II/ I I 0008. Exam I 4. Gaseous nitric oxide (NO. 3.4 L. 2.8 atm) and molecular oxygen (0;. l2 L. 0.63 mm) are separated as shown in the apparatus below. Calculate the new pressure inside the apparatus after the valve is opened and the two gases mix. Assume that the temperature remains constant at 22.0 °C. [5 pts] The. Volume .hwca.5¢; lb 3.44,.I'zL = m a... p p. .w.) .. ~ J: ’ V; 341 1.2L 3.4L 2.88101 0.638tm ffio 2 3_ (“film ‘1,“L>— 4.0 7 4.7444 ’00:. ' “‘3 “(m/J fn+~l :- PA’D 4:. [002's 4.97% 4— 0./5‘{a-¢w = 5. A weather balloon is filled with l85 L ol’a gas at 0.970 atm and 14.0 °C on the summit of Mt. Washington in New Hampshire. and then released into the atmosphere. After rising 4 miles into the atmosphere. the gas in the balloon expands to 1570 l, at a temperature of-l 1.0 °C. What is the atmospheric pressure at that altitude? [4 pts] I."O"LI.‘—/ .fi’ndv/ f o.}701~%u. ? = an = V IFJ'L 15-704 ’77' A -— conif. ‘— ID _ T; 7' H.232, 41.02; ,:~ 4 VF 21,—7- .. 175/- 41.02 «x732 PF - D'}7o“h‘ W794) [ahead-2.732: : (L Acetylene gas (Cszl is used for welding because it produces an extremely hot flame when burned in the presence of oxygen. Acetylene gas typically is stored in metal cylinders. How many grams of acetylene gas are present in a |25 L cylinder under a pressure ol’5.35 atmospheres at 25.0 °C'? [5 pts] ’9: V; 7:, / C; Fl,” 2) M)/ C_L/-/‘ _ PV = (53:61”) (MFA) n“"‘ T- (amazes (.152, 4- 2.732;.) “3"” we = lm/ “"‘l L a. .1 Z 3 win/4454 k) MacDonald. CHM! 020. III] 1/2008. limit: I 7. a. The density of an elemental gas is measured at 1.50 atm and 27.0 °C and found to be 1.95 g/L. Calculate the molar mass (M = g/mol) ofthe gas. [4 pts] MP -41” 43‘? =? M' ,0 M __ (L)! fl)<o.os’zoéfifi7¥f’-) ($7.02: 9- 1732) ’ IvS'Do-i-wr " 32.0f/u‘p/ 5.7L; 0“.L ou- b. What is the ms? [2 ts] Formula of gas = 0‘1 6 V. S t- P 8. Elodea is a green plant that carries out photosynthesis under water to produce glucose (CfiHQOh) and oxygen (03) as shown. In your lab. some Eladea plants produce 03 gas underwater that mixes with water vapor. You collect 344 mL ofthe resulting humidified 03 gas at 0.984 mm and 18.7 °C. 6 coztg) + 6 H30 (I) -) €511.20“ (mg) + 0 03(g) a. What is the partial pressure (in atm) of 02 gas in the sample it'the vapor pressure of water is 17.0 torr at 18.7 °C? [3 ms] Pnh/ = f’oA 4- ago 2 0.7é1 who: pm=_Oo,‘L “vim h. Calculate the mole fraction of 0: gas in the sample. [3 ptsl Ice 0 95.2 59,444 X0 = " —~... ' = o 97? * Pfi‘LI 0.9?‘1‘4-9‘351 ‘ x4: 0. 377' c. How many grams of CO; gas are required to produce 344 ml. ol‘ 0: gas? [3 pls] / 40A % Ma/ 40“ 7-? Mb/ 01 L. ’49 __ Poav = (9.)6247‘54) (JVVML I‘LOML 2. K1“ (amazes :3.“) (19:72: +3732) - o.<7/.3'J7»m/4)_1 Lu MacDonald. C I [M] 020, I l l I 1/2008, limm I 9. Which one of the following statements is incorrect for an ideal gas? Circle yottr answer. [3 ptsl a. Molecules of a gas collide with the walls of a container and exert pressure. b. Molecules of a as occupy no volume (have zero volume). c. Mo ecules of a . ave no mass d. Molecules of a gas are not attracted to each other. l0. At what conditions of P. T and n (moles) does a gas behave most like an ideal gas? Circle your an5wer. [3 ptsl a. high P. high T. high it b. low P. low T. low n c. high P. low T. high n d. low P. high T. high n e. low P. high T. low 11 | I. Consider three I 1. flasks at STP. Flask A contains NH3 gas. flask B contains N0; gas. and flask C contains N2 gas. Which flask contains the fewest number of molecules? Circle your answer. [3 pts] a. flask A h. flask B c. flask C d. the same number of molecules are present in all three flasks I2. In which flask above do the molecules have the highest kinetic energy? Circlc your answer. [3 pts] a. flask A b. flask B c. flask C d. the molecules have the same kinetic energy in all three flasks 13. Why does pressure increase when the temperature ofa mixture ol'Oz anti C 02 gases increases at constant volume? Circle your answer. [3 pts] a. The average velocity of 02 and CO2 molecules increases so they strike the wall of the container more often. b. hc surface area 0 t te wal s o t ic container increases so I e um ecules strike the walls more often. c. The kinetic energy of the CO; molecules is greater than the kinetic energy of the O2 molecules because (‘0: molecules have greater mass. d. None of the answers is correct. 14. According to Kinetic Molecular Theory of gases. what would happen to a closed sample ol‘a gas in which the temperature was increased while the volume was decreased. I3 pts] :1. The pressure would remain constant. b. The pressure would decrease. d. The number of moles of the gas would decrease. IS. Which law describes the relationship between pressure and volume of an ideal gas at constant temperature? Circle your answer. l3 ptsl a. Avagatlro‘s Law c. Amonton‘s Law d. Charlc's Law 16. Increasing the temperature ot'a sample of gas will affect the density ofthc gas in what way‘.’ Circle your answer. [3 ptsl x-affv‘w4- 4“! We .3 an em?“ “ ‘ 'fuolum¢ . . . m I a. density \vdl increase * ‘1‘- c c “a” _'_ ' . [-5 Volt)“ .3 congi‘togt' 17. Two dtllerent gases lit the same container may exert dtllerent pressures but may not have dillcrenl tcmperaturcs or occupy different volumes. Circle your answer. [3 ptsl I8. Mercury in a barometer rises 760 mm at sea level on a sunny day. Ifa low-pressure weather system train) moves into the area. will the level ol‘ mercury increase or decrease? Circle your answer. [3 ptsl a. increase ...
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This note was uploaded on 09/01/2010 for the course BB 10294 taught by Professor Politz during the Spring '10 term at WPI.

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ch1020_2008b_exam1solns - MacDonald. CHMIUZO. I ll] 1/2008....

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