Question

A)Consider the following gases, all at STP: Ne, SF6, N2, CH4.

Which gas is most likely to depart from assumption 3 of the kinetic molecular theory (Attractive and repulsive forces between gas molecules are negligible.)?

Which one is closest to an ideal gas in its behavior?

Which one has the highest root-mean-square molecular speed?

Which one has the highest total molecular volume relative to the space occupied by the gas?

Which has the highest average kinetic molecular energy?

Which one would effuse more rapidly than N2?

B) A mixture of gases contains 0.75mol N2, 0.35mol O2, and 0.20mol CO2. The total pressure of the mixture is 1.57atm .

What is the partial pressure of O2?

What is the partial pressure of CO2?

C) What is the partial pressure in atm of O2 of this mixture if it is held in a 12.60?L vessel at 14?C? (O2 =.149mole)

What is the partial pressure in atm of N2 of this mixture if it is held in a 12.60?L vessel at 14?C? (N2= .241mole)

What is the partial pressure in atm of H2 of this mixture if it is held in a 12.60?L vessel at 14?C?(H2= .610mole)

Answer 1

A)

i) it should be the larger molecule SF6

ii) the one closet to the ideal behaviour will be the smallest molecule

so Ne is the closet to ideal

iii)

we know that

RMS speed = sqrt ( 3RT/M)

so

lower the molecular mass . higher the speed

so

CH4 has the highest RMS speed

iv)

higher the molar mass , higher the molecular volume

so

SF6 has the highest total molecular volume

v)

we know that

average K.E = 1.5 x k x T

so it depends on temperature

so

at a given temp , all of them have the same average K.E

v1)

we know that

lower the molecular mass higher the effusion

from the given molecules

CH4 and Ne have less molecular mass than N2

so

Ch4 and Ne would effuse more than N2

B)

total moles = 0.75 + 0.35 + 0.2

total moles = 1.3

total pressure = 1.57

we know that

mole fraction = ( moles of component / total moles )

so

mole fraction of N2 = 0.75 / 1.3 = 0.577

mole fraction of O2 = 0.35 / 1.3 = 0.269

mole fraction og C02 = 0.2 / 1.3 = 0.154

now

partial pressure = mole fraction x total pressure

so

partial pressure of 02 = 0.269 x 1.57 = 0.4223 atm

parital pressure of C02 = 0.154 x 1.57= 0.24178 atm

C)

we know that

PV = nRT

given

V = 12.6 L

T - 287 K

so

for 02 :

PV = nRT

P x 12.6 = 0.35 x 0.0821 x 287

P =0.6545

so the partial pressure of 02 is 0.6545 atm

for C02 :

PV = nRT

P x 12.6 = 0.2 x 0.0821 x 287

P = 0.374

so the partial pressure of C02 is 0.374 atm

for N2 :

PV = nRT

P x 12.6 = 0.75 x 0.0821 x 287

P = 1.4025

so the partial pressure of N2 is 1.4025 atm