Chapter 7 Homework + recap

VSEPR review on molecular geometry

CH4

NH3

CH2O

CH3OH (C as center)

CO2

SO2

tetrahedral

trigonal pyramidal

trigonal planar

tetrahedral

Linear

Bent

A gas sample is collected in a balloon. The density of the gas sample will ? as the sample is heated. This is an example of ?

decrease, Charles's Law

A gas sample is collected in a balloon. The density of the gas sample will ? as the sample is under lower pressure. This is an example of ???

reduces, Boyle's law

The propane gas is stored in a rigid steel tank. The pressure of the gas will ? as the tank gets colder. This is an example of ????

decrease, Gay-Lussac's law

Arrange the states in order of increasing energy of the particles (highest to lowest).

solid, liquid, gas

Identify the intermolecular forces (IMF) for each pure liquid.

CH₄

HCl

NH₃

CH₂O

CH₃OH

CO₂

SO₂

molecular polarity Hydrogen bonding

nonpolar no

polar no

polar yes

polar no

polar yes

nonpolar no

polar no

About intermolecular forces

• attraction between polar molecules

• attraction between molecules with N-H, or O-H, or F-H bonds

• attraction between any two molecules due to induced dipole interaction

• attraction between any molecules with H atoms

• attraction between dipole moment and ion

• existing between any molecules

• dipole dipole interaction

• hydrogen bonding

• dispersion force

• invalid

• invalid

• dispersion force

Based on your answer on the previous question, fill "higher" or "lower":

NH₃ will have ? boiling point than CH₄

HCl will have ? melting point than CH₃OH

Carbon dioxide has ? boiling point than sulfur dioxide

Higher, lower, lower

The vapor pressure of a liquid ___________ with increasing temperature

increases

Identify the state based on the physical properties

• finite volume, indefinite shape, incompressible

• finite volume, finite shape, incompressible

• indefinite volume, indefinite shape, compressible

• liquid

• solid

• gas

Strong intermolecular force (IMF) causes

? vapor pressure,

? viscosity, and

? boiling point/melting point

• low

• high

• high

Kinetic Molecular Theory

• There is a large distance between gas particles as compared to their relative size.

• Gas particles collide with each other and surfaces without losing any energy.

• The average kinetic energy of the molecules of a gas is proportional to the temperature of the gas in kelvins.

• Gas particles do not repel or attract each other.

Which of the following gases is least likely to behave ideally?

Low temperature and high pressure

Rank the density of following gases: neon gas, fluorine gas, hydrogen gas

fluorine gas, neon gas , hydrogen gas

At constant temperature, as its volume increases, the pressure of gas will

decrease

At at constant pressure, as its temperature increases, the volume of gas will

increase

At at constant volume, as its temperature increases, the pressure of gas will

increase

The partial pressure of gas A in a gaseous mixture is proportional to

the mole fraction of gas A in the mixture

About ideal gas law   P x V = n x R x T

P=

V=

n=

R=

T=

atmosphere aka atm

liter aka L

mole of gas

0.08206 / 0.0821 atm x L / mol x K
kelvin aka K

About combined gas law: P1 x V1 / T1 = P2 x V2 / T2

P1=

V1=

T1=

unit of temperature

P2 x V2 x T1 / V1 x T2

P2 x V2 x T2 / P2 x T1

P1 x V1 x T2/ P2 x V2

kelvin

Convert 1.744 atm to mmHg (millimeter mercury)

1.744 atm x 760 mmHg / 1 atm = 1.325 mmHg

Convert 5.902 atm to mmHg

1 atm = 760 mmHg

5.902 atm X 760 mmHg / 1 atm = 4485.52 mmHg

Convert 506.58 mmHg to atmosphere

506.58 mmHg X 1 atm / 760 mmHg = 0.6666 atm.

2500 liters of oxygen gas is produced at 1.00 atm of pressure. It is to be compressed and stored in a 118 liter cylinder. If temperature is constant, the final pressure of the oxygen in the cylinder will be ? atm.

• P1​=1.00 atm

• V1​=2500 liters

• V2​=118 liters

P2​= (1.00 atm) X (2500 liters) / 118 liters ≈ 21.2 atm

100 liters of oxygen gas is produced at 1.00 atm of pressure. It is then stored in a 13 liter cylinder. If temperature is constant, the final pressure of the oxygen in the cylinder will be _________ atm.

P2 = (P1 x V1)/ V2

P2= (1.00 atm x 100 L ) / 13 L = 7.69 atm

A balloon has a volume of 5.00 liters of 22°C and 1.00 atmosphere of pressure. If the pressure of the balloon is increased to 2.6 atm at 22°C, the volume of the balloon will be ____ liters.

• P1​=1.00 atm (initial pressure)

• V1​=5.00 liters (initial volume)

• P2​=2.6 atm (final pressure)

V2​= (1.00 atm) X (5.00 liters) / 2.6 atm = 1.92 liters

Convert 69 ^oC to Kelvin temperature

K= 69 + 273.15 K= 342.15

A gas sample has a volume of 500 mL at 81°C. At the same pressure, what is the temperature in Celsius degrees when the volume of gas becomes 250 mL?

• V1​=500 mL

• T1​=354.15 K

• V2​=250 mL

T1​(K)= 81 + 273.15 = 354.15 K

T2​= (250 mL) X (354.15 K) / 500 mL = 177.075 K​

T2​(°C)= 177.075 − 273.15= −96 C

The volume of 0.9 moles of gas at STP = ______ L

Volume= Number of moles × Molar volume at STP

0.9 moles × 22.4liters / 1 mole = 20.16 L

A mixture of helium, argon and krypton is made and stored in a cylinder at a total pressure of 2.80 atm. The partial pressure of helium is 900 torr, and that of argon is 168 torr. What is the partial pressure of krypton (in torr) in the mixture?

Ptotal​= 2.80 atm × 760 torr​ / 1 atm = 2128 torr

Pkrypton​= 2128 torr − 900 torr -168 torr​ = 1060

A gas sample collected at 35.0°C and a pressure of 710 torr has a volume of 200 mL. The temperature and pressure are changed, and the gas is compressed to 150 mL. The new temperature is 19°C; what is the new pressure in torr?

T1= 35.0 + 273.15= 308.15 k                 

T2= 19 + 273.15= 292.15K

(710 torr) (200mL) / 308.15 k = P2 (150mL) / 292.15K

(710 torr) X (200mL) X (292.15K)  / (308.15 k) X (150mL)

P2= 896.65 torr

Calculate the pressure (in atm) for 0.39 mol of N₂ gas in a 1.1 L container at 24°C.

K = 24 + 273.15 = 297.15 K

P= (0.39 mol) X (0.0821 L* atm/mol*K) X (297.15 K) / 1.1L = 8.64 atm 

The volume occupied by 8.22 g of SO₂ gas confined at a pressure of 721 torr at 25.0°C is __________ liters.  (hint: R = 0.0821 liter atm/mol K)

Molar mass SO2= 32.07 + 2 X 16.00 = 64.07 g/mol

P= 721 torr X 1 atm/ 760 torr = 0.9487 atm

n= 8.22g/ 64.07 g/mol = 0.1283 mol

K= 25.0 + 273.15= 298.15 K

V= (0.1283 mol) X (0.0821 L* atm/mol*K) X ( 298.15 K) / 0.9487 atm = 3.31L