Merrill Assignment 1(Hebden 4.5) Answers

7/28/2019 Merrill Assignment 1(Hebden 4.5) Answers

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Gases Practice Questions

These page numbers are from Merrill.

P. 472-473

#27, 28, 30(a), 31(a), 34, 36, 37(a), 40(a), 41(a), 43(a), 44, 47, 48, 50, 51, 53, 58

P. 494-496

#35, 36(a), 37(b), 39, 40, 41, 42, 43, 46, 53, 58, 62, 65

Answers

27. 0oC, 101.3 kPa, STP

28. temperature, volume and number of particles

30a. P1V1 = P2V2, V2 = P1V1/P2 = 80.8 kPa x 817 mL / 101.3 kPa = 651.7 = 652 mL

31a. P1V1 = P2V2, V2 = P1V1/P2 = .600 m3 x 110.0 kPa / 62.4 kPa = 1.0577 = 1.06 m3

34. P1V1 = P2V2, P2 = P1V1/V2 = 4.3 dm3 x 105.0 / 2.8 dm3 = 161.25 = 160 kPa

36. a. Over any body of water, some molecules are in the gas phase. This water vapour has a

pressure.

b. The observed pressure of a gas includes this water vapour pressure so it is artificially high.

c. Subtract the vapour pressure from the oxygen pressure to get oxygen’s actual pressure.

Vapour pressure depends on the temperature of the water so the temperature of the water must

be known (and the vapour pressure at different temperatures must be known, too)

37a. At 12oC, water vapour pressure is 1.4 kPa (p. 459) so dry pressure is 84.1 – 1.4 = 82.7

kPa.

P1V1 = P2V2, V2 = P1V1/P2 = 82.7 kPa x 871 mL / 101.3 kPa = 711.07 mL = 711 mL

40a. V1/T1 = V2/T2, V2 = V1T2/T1 (T in K), V2 = 5.93 mL x 273 K / 492 K = 3.2904 mL = 3.29

mL

41a. V1/T1 = V2/T2, V2 = V1T2/T1 (T in K), V2 = 2.97 m3 x 502 K / (72 + 273)K = 4.3215 m3 =

4.3 m3.

43a. PV/T = P2V2/T2, V2 = PVT2/P2T = 654 mL x 65.3 kPa x 277 / (108.7 kPa x 279) = 390.06

mL = 390. L

44. PV/T = P2V2/T2, V2 = PVT2/P2T = 101.3 kPa x 325 mL x 293 K / (93.3 kPa x 273 K) =

378.718 mL = 379 mL

47. PV/T = P2V2/T2, P2 = PVT2/V2T = 99.7 kPa x .00304 m3 x 298 K / (.00325 m3 x 285 K) =

97.511 kPa = 97.5 kPa



48. Diffusion is the movement of material from high concentration (pressure) to low

concentration. Effusion is the movement of gas through a small opening. (This is hardly

important but it is one of those trivia questions.)

50. a. CO2 b. C3H8 c. N2 d. SO3

51. KE is related to temperature. If two gases are at the same temperature, they must have the

same average kinetic energy. (m1/m2)-1/2 = v2/v1 ( mO2/mHe)-1/2 = vHe/vO2, (32/4)-1/2 = 2.828

53. Low pressure, high temperature (normal pressure and temperature)

58. a. v/2 b. 2V c. 4V d. 2/3V e. V f. 1/4V g. 3/8V h. 5/16 V

P. 494

35. 22.4 L

36a. moles = vol of gas/22.4 L/mol = 168 L/22.4 L/mol = 7.5 mol

37b. vol of gas = 22.4 L/mol x mol = 22.4 L/mol x .00545 = .12208 L = .122 L

39. PV = nRT, P = nRT/V, P = 0.400 mol x 8.31 LkPa/Kmol x 300 K / 10.0 L = 99.72 kPa = 99.7

kPa

40. PV = nRT, n = PV/RT, n = 389 kPa x (104 m3 x 1000L/m3) / 8.31 LkPa/Kmol x 298 K =

16336.7 mol = 1.63 x 104 mol

41. PV = nRT, V = nRT/P, V = 12 mol x 8.31 LkPa/Kmol x 325 K / 500 kPa = 64.818 L = 65 L

42. PV = nRT, T = PV/nR, T = 200 kPa x 10.9 L / .877 mol x 8.31 LkPa/Kmol = 299.13 K = 299

K

43. MM = mass/mol. n = PV/RT, 105 kPa x .500 L / 8.31 LkPa/Kmol x 250 K = .02527 mol

MM = 1.00 g / .02527 mol = 39.57 g/mol = 40. g/mol



46.

Fe2O3 + 3CO 2Fe + 3CO2

Mass 15.7 g

Mm 159.6 g/mol

Mol .098371 mol .29511

Vol

Conc

Since it is at STP, .29511 mol x 22.4 L/mol = 6.6105 L = 6.61 L

53a

2ZnS + 3O2 2ZnO + 2SO2

Mass 418 g 348.976

Mm 97.5 g/mol 81.4

Mol 4.287 mol 8.258 4.287

Vol 185 L

LR 2.14 2.7529

349 g ZnO produced

2ZnS + 3O2 2ZnO + 2SO2

Mass 4.66 g

Mm 97.5 g/mol

Mol .04779 mol .05580 .03720

Vol 1.25 L

LR .023897 .0186

Since it is at STP, .03720 mol x 22.4 L/mol = .833333 L = .833 L

58



2Ag + Cl2 2AgCl

M 2.51

Mm 107.9

Mol .02326 .01163

Vol

P 99.2

T 297

V = nRT/P = .01163 x 8.31 LkPa/Kmol x 297 K / 99.2 kPa = .28938 L = .289 L

62. a. LR = iron b. LR = oxygen c. LR = ? iron? d. LR = Charcoal

65. Total Volume = vol argon + vol hydrogen + vol nitrogen

V = mol / 22.4 L V = M/mm/22.4 L/mol, Vargon = 1.5g / 39.9g/mol / 22.4 L/mol = .001678 L

mol = M/mm VH2 = .05 g / 2 g/mol / 22.4 L/mol = .001116 L

VN2 = 0.25 g / 28 g/mol /22.4 L/mol = .0003986

Total Volume = .0031926 L = .0032 L

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Merrill Assignment 1(Hebden 4.5) Answers