LECTURE 41 WRITING COMPOUND FORMULAS



13-01

UNIT 13 - LECTURE 63: IDEAL GAS LAW: P V = n R T

A. P = pressure

1. P = force / area

a. lbs / in2 1 atm = 14.7 psi

b. N / m2 1 atm = 101,325 Pa (pascals)

2. P = amount of liquid that the atmosphere can support

a. ~33 ft of water

b. 760 mm Hg = 760 torr Evangelisto Torricelli

(1608-1647)

|atm P |1 |14.7 |101,325 |~ 33 |760 |

|units |atm |psi |Pa |ft H2O |mm Hg |

3. Make the following conversions:

1. 3.21 atm = __2,440__ torr 2. 123,000 Pa = __17.8__ psi

CLASSWORK:

Make the following conversions:

_

1. 321 torr = ___6.21___ psi 2. 5.03 atm = _510,000_ Pa

13-02

B. V = volume

1. Standard molar volume: 22.4 L/moL at STP

C. n = moles

1. moles = g / MW 60.0 g CO2

1.35 mole CO2

44.0 g/mole

D. T = temperature . . . proportional to molecular speed Kinetic_Energy_in_a_Gas.mov

1. Standard temperature = 0 οC

Temperature Scale[pic]

2. Celcius οC = 5/9 ( οF - 32 ) οF = 9/5 οC + 32

3. K = οC + 273.15 οC = K - 273.15

4. Make the following conversions:

a. 321 K = _________ οC b. –123.4 οF = _________ οC _________ K

CLASSWORK:

Make the following conversions:

_

3. 123 K = _– 150_ οC 4. – 32.1 οC = _240.9 _ K

13-03

E. R = gas constant

1. Derive R in a variety of units:

P V P V P V

R = R = R =

n T n T n T

|62.4 torr L/moL K |62,400 torr mL/moL K |

|0.0821 atm L/moL K |82.1 atm mL/mol K |

|8.314 Joule/moL K |0.008314 kJ/moL K |

|Pa L/moL K |psi mL/mol K |

|Pa m3/moL K |psi m3/mol K |

CLASSWORK: [Note: 1,000L = 1 m3]

5. Derive R in: psi; m3; moles; K 6. Derive R in: psi; mL; moles; K

P V P V

R = R =

n T n T

7. Derive R in: Pa; m3; mole; K. 8. Derive R in: Pa; L; mole; K.

P V P V

R = R =

n T n T

F. P V = n R T problems:

a. Determine the volume of a flask in mL if it contains 1.00 mole at 20.0 οC

and 13.54 psi. ANS: 26,200 mL

P V = n R T

b. A 13,500 mL flask contains 2.00 moles of a gas at 20.0 οC. Determine

the pressure in this flask in Pa. ANS: 361,000 Pa

P V = n R T

13-04

c. A 20.0 L flask contains 0.423 moles of gas at 800.0 torr. Determine the

temperature in οC. [Note: solve in K; convert to οC] ANS: 333 οC

P V = n R T

d. A 25.0 L flask contains CO gas at 20.0 οC and 1.25 atm. Determine

the number of moles of CO in this flask. ANS: 1.30 moles

P V = n R T

CLASSWORK:

9. Calculate the volume in mL of 0.0250 moles of N2 gas at 31οC and 1.10 atm.

P V = n R T

10. Calculate the pressure in atm of 0.600 moles of N2 gas occupying a 12.0 L

cylinder at 35οC.

P V = n R T

11. Calculate the temperature in οC of 0.310 moles of N2 gas occupying a 10.0 L

cylinder at 703 torr.

P V = n R T

12. Calculate the number of moles of N2 gas occupying a 6.00 L cylinder at 27οC

and 811 torr.

P V = n R T

13-05

UNIT 13 - LECTURE 64: INDIVIDUAL GAS LAWS - BOYLE

1. Graphical Analysis:

a. X Y = 100 . . . indirect relationship

50 *

|X |Y |

|2 |50 |

|5 |20 |

|10 |10 |

|20 |5 |

40

30

20 *

10 *

*

0

0 5 10 15 20

b. X = 5 Y . . . direct relationship

|X |Y |

|10 |2 |

|20 |4 |

|30 |6 |

|40 |8 |

|50 |10 |

10 *

8 *

6 *

4 *

2 *

0

0 10 20 30 40 50

2. BOYLE’S LAW: ΔP vs ΔV . . . constant: n,T P-V_Relationships.mov 13-06

a. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the volume if the pressure is changed to 3.21 atm at constant temperature. ANS: 132 mL

P V = n R T

Robert Boyle (1627-1691)

b. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the

volume if the pressure is changed to 654 torr. ANS: 493 mL

P V = n R T

c. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the

pressure required to change the volume to 6.54 L. ANS: 0.0649 atm

P V = n R T

CLASSWORK:

_

13. A sample of gas has a volume of 390 mL when measured at 25οC and

760 torr. What volume in mL will it occupy at 25οC and 195 torr.

P V = n R T

_

14. A sample of gas has a volume of 410 mL when measured at 11οC and

380 torr. What volume in mL will it occupy at 11oC and 2.00 atm.

P V = n R T

13-07

15. What final pressure in torr must be applied to a sample of gas having a

volume of 195 mL at 20οC and 759 torr to permit the expansion to a

volume of 675 mL at 20οC.

P V = n R T

16. The volume of a gas is 10.0 L at 10.0 atm and 273 K. Calculate the

pressure in torr if its volume is changed to 565 mL while the temperature

remains constant.

P V = n R T

UNIT 13 - LECTURE 65: INDIVIDUAL GAS LAWS - CHARLES

1. CHARLES’ LAW: ΔT vs ΔV . . . constant: n,P Charles_Law[1].ram

a. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the volume in mL if the temperature is changed to 34.6 οC atm at constant pressure. ANS: 358 mL

P V = n R T

Jacques Charles (1746-1823)

b. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the

temperature in οC required to change the volume to 0.654 L. ANS: 289 οC

P V = n R T

CLASSWORK: 13-08

17. A sample of gas has a volume of 222 mL when measured at 11οC and

750 torr. What volume in mL will it occupy at 22οC and 750 torr.

P V = n R T

18. A sample of gas has a volume of 90.0 mL when measured at 27οC and

740 torr. What volume in mL will it occupy at 5οC and 740 torr.

P V = n R T

19. A sample of gas has a volume of 120.0 mL when measured at 27οC and

630 torr. What temperature in oC will the volume be 80.0 mL at

constant pressure.

P V = n R T

20. A sample of gas has a volume of 206 mL when measured at 31οC. What

temperature in οF will the volume be 602 mL at constant pressure.

[οF = 9/5 οC + 32]

P V = n R T

UNIT 13 - LECTURE 66: INDIVIDUAL GAS LAWS - GAY-LUSSAC 13-09

1. GAY-LUSSAC’S LAW: ΔT vs ΔP . . . constant: n,V

a. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the temperature in οC if the pressure is changed to 3.21 atm at constant volume. ANS: 501 οC

P V = n R T

Joseph Gay-Lussac (1778-1850)

b. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the

pressure in torr if the temperature is reduced to 12.3 οC at constant

volume. ANS: 897 torr

P V = n R T

CLASSWORK:

21. A sample of gas has a volume of 10.0 L when measured at 27 οC and

111 torr. Determine the pressure in torr if the temperature is changed

to 127 οC at constant volume.

P V = n R T

22. The temperature of 200 mL of a gas originally at STP is changed to

-25 οC at constant volume. Calculate the final pressure in torr.

P V = n R T

23. A sample of gas has a volume of 50.0 mL when measured at 27 οC and

639 torr. At what temperature in οC will the pressure be 775 torr at

constant volume.

P V = n R T

24. A sample of gas has a volume of 5.00 L when measured at 707 torr and

33 οC. At what temperature in οC will the pressure be 624 torr at

constant volume.

P V = n R T

UNIT 13 - LECTURE 67: INDIVIDUAL GAS LAWS – COMBINED 13-10

a. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the

temperature in οC if the pressure is changed to 765 torr and the volume

is increased to 0.456 L. ANS: 322 K (or) 49οC

P V = n R T

b. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the pressure if the temperature is reduced to 12.3 οC and the volume is reduced to 0.200 L. ANS: 2.04 atm

P V = n R T

c. A gas has a volume of 345 mL at 23.5 οC and 1.23 atm. Determine the

STP volume. ANS: 391 mL

P V = n R T

CLASSWORK:

25. A sample of gas has a volume of 503 mL when measured at 28 οC and

740 torr. Determine the volume at STP.

P V = n R T

26. A sample of gas has a volume of 195 mL when measured at 21 οC and

1.00 atm. Determine the volume at 66oC and 608 mmHg.

P V = n R T

27. A sample of gas has a volume of 245 mL when measured at 25 οC and

619 torr. Calculate its volume in mL at STP.

P V = n R T

13-11

28. A sample of gas has a volume of 5.10 L when measured at 640 torr

and 27 οC. Its volume is compressed to 2.10 L at 105 οC. Determine the

pressure in torr.

P V = n R T

29. A sample of gas has a volume of 317 mL when measured at STP.

Determine the pressure in atm if the volume expands to 456 mL at a

temperature of 55 οC.

P V = n R T

30. A sample of gas has a volume of 4.40 L when measured at 69 οC and

1.00 atm. Determine its pressure in atm if the new volume is 5.00 L at

27 οC.

P V = n R T

31. A sample of gas has a volume of 152 mL when measured at STP.

Calculate it temperature in οC if the volume expands to 329 mL when

the pressure is changed to 951 torr.

P V = n R T

32. A sample of gas has a volume of 125 mL when measured at 643 torr and

57 οC. Calculate it temperature in οC if the volume is increased to 325 mL

when the pressure is decreased to 597 torr.

P V = n R T

33. A sample of gas has a volume of 2.50 L when measured at 1.00 atm and

27 οC. Calculate the pressure in atm required to decrease the volume to

2.00 L when the temperature is decreased to 24 οC.

P V = n R T

UNIT 13 - LECTURE 68: PV = nRT RELATED PROBLEMS 13-12

1. Develop:

a. PV = gRT / MW

1) Determine the mass of He in the blimp pictured above if its volume is 1000 m3 (1 m3 = 1,000 L) at ambient conditions:

P = 567 torr ; T = 5 οC. ANS: 131,000 g

g R T

P V = ---------------------

MW

2). Assuming most of the matter in a galaxy is H2, determine

the STP volume of the galaxy pictured below if its mass is

1.78x1062 grams. [R = 8.21x10–5 atm-m3/moL-K]

ANS: 1.99x1060 m3

g R T

P V = ---------------------

MW

3) If 686 mL of gas measured at 25 οC and 731 torr has a mass of

2.3456 g, determine its MW and identify it from the choices.

g R T

P V = ---------------------

MW

a) Cl2 b) HCl c) Cl2O d) NOCl e) PCl3

71.0 36.5 87.0 65.5 137.5

CLASSWORK: 13-13

_

34. If 485 mL of gas measured at 30 οC and 600.0 torr has a mass of 2.0162 g,

determine its MW and identify it from the list of possible choices.

g R T

P V = --------------------- MW = ________

MW

a) He b) Ne c) Ar d) Kr e) Xe f) Rn

_

35. If 0.972 L of gas measured at 50 οC and 1.23 atm has a mass of 0.9017 g,

determine its MW and identify it from the list of possible choices.

g R T

P V = --------------------- MW = ________

MW

a) HF b) HCl c) HBr d) HI e) HAt

36. A sample of N2O3 gas measured at 33 οC and 15.0 psi occupies a volume of

485 mL. Determine the mass of this N2O3 sample in g.

g R T

P V = --------------------- g = ________

MW

37. A 1.000 g sample of N2O gas is measured at 33 οC and 135,000 Pa. Determine

the volume of this N2O sample in mL.

g R T

P V = --------------------- V = ________

MW

38. A 101.0 g sample of NO gas is measured 1.23 atm and has a volume of

25.9 L. Determine the temperature of this NO sample in οC.

g R T

P V = --------------------- T = ________

MW

13-14

39. A 1.479 g sample of N2O4 gas is measured at –73 οC and has a volume of

321 mL. Determine the pressure of this NO sample in torr.

g R T

P V = --------------------- P = ________

MW

UNIT 13 - LECTURE 69: PV = nRT RELATED PROBLEMS

1. Develop:

b. P = dRT / MW

1) Calculate the temperature

of the CO2 gas in οC if the

density of the CO2 in the

paintball gun pictured above is 5.35 g/L at 3.00 atm.

ANS: 27.5 οC

d R T

P = ---------------------------

MW

2) Determine the density (g/L) of the propane gas (C3H8) in one

of the above tanks if the internal pressure is 10.0 atm at 34οC.

ANS: 17.5 g/L

d R T

P = -------------------------

MW

13-15

3) Determine the pressure of the air in psi

in one of the tires in the 18-wheeler

pictured if the density is 1.31 g/L at 22 οC.

[Assuming air is 80% N2 and 20% O2,

the MW of air is 28.8 g/mole]

ANS: 16.2 psi

d R T

P = -------------------------

MW

CLASSWORK:

40. Calculate the d of CH4 gas in g/L at –45 οC and 303 torr.

d R T

P = ---------------------------

MW

41. Calculate the dSTP of Br2 gas.

d R T

P = ---------------------------

MW

_ _

42. A gas has a d=1.849 g/L at 30 οC and 460 torr. Determine its MW and

identify it from the list of possible choices.

d R T

P = ---------------------------

MW

a) N2O b) NO2 c) N2O3 d) N2O4 e) N2O5

13-16

43. Calculate the pressure of CH4 gas in Pa at – 5 οC if its density is 4.19 g/L.

d R T

P = ---------------------------

MW

44. Calculate the temperature in οC of a Br2 vapor sample at 11.1 psi if its

density is 4.62 g/L .

d R T

P = ---------------------------

MW

13-17

UNIT 13 - LECTURE 69: GAS LAWS VS STOICHIOMETRY

1. Determine the number of grams of NaN3 that are required to fill an auto air

bag with N2 to a volume of 15.0 L at 23 οC and 1.23 atm. Airbags.mov

ANS: 32.9 g

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) P V = n R T

b) 2 NaN3(s) 2 Na(s) + 3 N2(g)

65.0

2. Determine the volume of O2 gas that will be produced by decomposing

123.45 g of KClO3 at 34.5 οC and 789 torr. ANS: 36.7 L

[Note – gas law question is asked: stoichiometry 1st; gas laws 2nd]

a) 2 KClO3(s) 2 KCl(s) + 3 O2(g)

122.6

b) P V = n R T

CLASSWORK: 13-18

45. Determine the number of grams of HgO that are needed to produce 214.3 mL

of O2 at 27 οC and 753.1 torr.

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) P V = n R T

b) 2 HgO(s) 2 Hg(l) + O2(g)

216.6

46. Determine the volume of N2 gas in L that will be produced by decomposing

23.45 g of (NH4)2Cr2O7 at 24.3 οC and 809 torr.

[Note – gas law question is asked: stoichiometry 1st; gas laws 2nd]

a) (NH4)2Cr2O7(s) Cr2O3(s) + N2(g) + 4H2O(l) 252.0

b) P V = n R T

13-19

UNIT 13 - LECTURE 70: GASES COLLECTED “OVER WATER”

1. Collecting Gases “over water”

[pic]

beginning of Rx at Rx completion

a. Three possible outcomes:

A B C

PG PG PG

LD

PG < PATM PG = PATM PG > PATM

1) Situation C can be made to be like B: PG = barometer . . . DEMO.

2) In situation A above, PG = barometer reading - LD

3) LD is measured in mm H2O. In order to subtract, the units must

be converted to the units of the barometer (mm Hg or torr). Since

Hg is 13.6 times denser than water, divide the LD by 13.6 before

subtracting from the barometer reading.

b. Dalton’s Law:

1) gases collected “over water” are mixtures of the gas from the

chemical reaction with water vapor mixed in.

2) PTOTAL = PGAS + PH2O

c. Typical Dalton’s Law problems: 13-20

1) 45.6 mL of O2 is collected over water when P = 753.8 torr and

T = 25 οC. Determine the mass of H2O2 that decomposed.

ANS: 0.122 g

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) Determine the pressure of the “dry” O2:

Pbarometer

– LD / 13.6

– PH2O [See: Table below]

b) Determine the VSTP of the O2 that was collected:

P V = n R T

c) Determine the mass of H2O2 that decomposed:

2 H2O2 H2O + O2

34.0

13-21

2) 43.2 mL of CO2 is collected over water when P = 789.4 torr and

T = 24 οC. The LD is 81.6 mm. Determine the mass of Al2(CO3)3

that decomposed. ANS: 0.139 g

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) Determine the pressure of the “dry” O2:

Pbarometer

– LD / 13.6

– PH2O [See: Table below]

b) Determine the VSTP of the CO2 that was collected:

P V = n R T

c) Determine the mass of Al2(CO3)3 that decomposed:

Al2(CO3)3 Al2O3 + 3 CO2

234.0

13-22

3) Determine the volume of C2H2 in mL that will be collected over

water when 1.83 g of CaC2 reacts with excess water at 778.8 torr

and 28.0 οC. The LD is 95.2 mm. ANS: 721 mL

[Note – gas law question is asked: stoichiometry 1st; gas laws 2nd]

a) Determine the VSTP of C2H2 that will be produced:

CaC2 + 2 H2O C2H2 + Ca(OH)2

64.1

b) Determine the pressure of the “dry” C2H2:

Pbarometer

– LD / 13.6

– PH2O [See: Table below]

c) Determine the non – VSTP of the CO2 that was collected:

P V = n R T

CLASSWORK: 13-23

47. 43.2 mL of O2 is collected over water when P = 777.2 torr and T = 26 οC.

The LD is 136.0 mm. Determine the mass of WO3 that decomposed.

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) Determine the pressure of the “dry” H2:

Pbarometer

– LD / 13.6

– PH2O [See: Table below]

b) Determine the VSTP of the O2 that was collected:

P V = n R T

c) Determine the mass of WO3 that decomposed:

2 WO3 2 W + 3 O2

231.9

13-24

48. 45.6 mL of H2 is collected over water when P = 780.9 torr and T = 22 οC.

Determine the mass of AlH3 that decomposed.

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) Determine the pressure of the “dry” H2:

Pbarometer

– LD / 13.6

– PH2O [See: Table below]

b) Determine the VSTP of the H2 that was collected:

P V = n R T

c) Determine the mass of AlH3 that decomposed:

2 AlH3 Al + 3 H2

30.0

13-25

49. Determine the volume of PH3 in mL that will be collected over water when

0.123 g of AlP reacts with excess water at 789.6 torr and 29.0 οC. The LD is

122.4 mm.

[Note – gas law question is asked: stoichiometry 1st; gas laws 2nd]

a) Determine the VSTP of PH3 that will be produced:

AlP + 3 H2O PH3 + Al(OH)3

58.0

b) Determine the pressure of the “dry” PH3:

Pbarometer

– LD / 13.6

– PH2O [See: Table below]

c) Determine the non – VSTP of the PH3 that was collected:

P V = n R T

UNIT 13 - LECTURE 71: MV AND METAL IDENTIFICATION 13-26

1. Determine the experimental value of the MV of SO3 if 128.0 g of NaHSO4

decomposed to produce 12.3 L of SO3 collected over water at 40.0 οC and

908.4 torr.

a) stoichiometry moles of SO3

2 NaHSO4 Na2SO4 + H2O + SO3

120.1

b) gas laws VSTP of SO3

Pbarometer

– LD / 13.6

– PH2O

P V = n R T

VSTP

c) MV (SO3) = ------------

moles

13-27

2. When 0.4469 g of an unknown metal completely reacts with HCl, 468 mL

of H2 are collected over water at 25.0 οC and 773.2 torr. The LD was

108.8 mm. Determine the MW of this unknown metal and identify it.

LD

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) Determine the pressure of the “dry” H2:

Pbarometer

– LD / 13.6

– PH2O

b) Determine the VSTP of the

H2 that was collected:

P V = n R T

c) Determine the moles of metal that reacted:

M + 4 HCl MCl4 + 2 H2

g metal

d) metal MW = ---------------------

moles of metal

e) identify unk metal: a) 22Ti b) 32Ge c) 42Mo d) 50Sn e) 82Pb

CLASSWORK: 13-28

50. Determine the experimental value of the MV of NH3 if 4.4018 g of (NH4)3N

decomposed to produce 6.30 L of NH3 collected over water at 30.0 οC and

808.8 torr.

a) stoichiometry moles of NH3

(NH4)3N 4 NH3

68.0

b) gas laws VSTP of NH3

Pbarometer

– LD / 13.6

– PH2O

P V = n R T

VSTP

c) MV (NH3) = ------------

moles

13-29

51. When 0.0847 g of an unknown metal completely reacts with H3PO4, 50.0 mL

of H2 are collected over water at 20.0 οC and 790.5 torr. The LD was

27.2 mm. Determine the MW of this unknown metal and identify it.

LD

[Note - stoichiometry question is asked: gas laws 1st; stoichiometry 2nd]

a) Determine the pressure of the “dry” H2:

Pbarometer

– LD / 13.6

– PH2O

b) Determine the VSTP of the

H2 that was collected:

P V = n R T

c) Determine the moles of metal that reacted:

3 M + 2 H3PO4 M3(PO4)2 + 3 H2

g metal

d) metal MW = ---------------------

moles of metal

e) identify unk metal: a) 4Be b) 12Mg c) 20Ca d) 38Sr e) 56Ba

13-30

UNIT 13 – CLASSWORK ANSWERS

1. 6.21 psi 2. 5.10x105 Pa 3. 51 οC 4. – 190.1 οF and 149.6 K

5. 0.00121 psi m3/mol K 6. 1,210 psi mL/mol K 7. 8.31 Pa m3/mol K

_

8. 8,310 Pa L/mol K 9. 567 10. 1.26 11. 90 12. 0.260

13. 1,520 14. 103 15. 219 16. 135,000 17. 231 18. 83.4 19. –73

20. 1,139 21. 148 22. 690 23. 91 24. –3 25. 444 26. 281

27. 183 28. 1,960 29. 0.835 30. 0.772 31. 466 32. 524 33. 1.24

34. Xe 35. HF 36. 1.49 37. 428 38. –158 39. 625 40. 0.341

41. 7.13 42. N2O3 43. 583,000 44. 44.0 45. 3.73 46. 2.13

47. 0.266 g 48. 0.0378 g 49. 53.2 50. 22.5 L/mole 51. c (Ca)

UNIT 13 Pretest 13-31

1. Derive R in: inHg; ft3; moles; K [Note: 1 L = 0.0353 ft3]

2. A 20.0 L flask contains 1.523 moles of gas at 13.5 psi. Determine the

temperature in οC.

3. The volume of a gas is 909 mL at 159,000 Pa and 273 K. Calculate the

pressure in torr if its volume is changed to 565 mL while the temperature

remains constant.

4. A sample of gas has a volume of 217 mL when measured at –11οC and

760 torr. What volume in mL will it occupy STP.

5. A sample of gas in a steel ball has a volume of 543 mL when measured at

767 torr and 33οC. At what temperature in οC will the pressure be 656 torr.

6. A sample of gas has a volume of 1.25 L when measured at 643 torr and

47 οC. Calculate it temperature in οC if the volume is increased to 3.20 L

when the pressure is decreased to 497 torr.

7. If 0.972 L of gas measured at 50 οC and 12.3 psi has a mass of 3.9645 g,

determine its MW and identify it from the list of possible choices.

a) H2O b) H2S c) H2Se d) H2Te

8. Calculate the density of CH4 gas in g/L at – 15 οC and 703 torr.

9. Determine the volume of O2 gas in mL that will be produced by decomposing

0.2345 g of H2O2 at 24.5 οC and 689 torr.

2 H2O2(aq) 2 H2O (l) + O2(g)

34.0

P V = n R T

10. 43.2 mL of N2O3 is collected over water when P = 769.7 torr and T = 27 οC.

The LD is 149.6 mm. Determine the mass of Mn(NO2)6 that decomposed.

P V = n R T

Mn(NO2)6 3 N2O3 + MnO3

330.9

13-32

11. When 0.3150 g of an unknown metal completely reacts with H2SO4, 168 mL

of H2 are collected over water at 25.0 οC and 779.8 torr. The LD was

68.0 mm. Determine the MW of this unknown metal and identify it.

P V = n R T

2 M + 3 H2SO4 M2(SO4)3 + 3 H2

g metal

metal MW = ---------------------

moles of metal

a) 13Al b) 24Cr c) 26Fe d) 27Co e) 31Ga

Pretest Answers:

1. 0.0867 inHg ft3/mole K 2. – 126 οC 3. 1,920 torr 4. 226 mL

_

5. – 11 οC 6. 360 οC 7. d (H2Te) 8. 0.699 g/L 9. 78.1 mL

10. 0.187 g 11. e (Ga)

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