# Comparison of the Modes of Mass Transfer

This quiz contains multiple-choice problems on concepts of velocity and concentration, convective mass transfer, Fick’s law, Schmidt number, density concepts, emissivity and melting point.

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The ratio of number of moles of species A to the total number of moles of the mixture is known as

Mole fraction Mass fraction Partial pressure Mass density

A solution contains 0.3 moles of solute A, 0.2 moles of B and 0.5 moles of C. What will be the mole fraction of A in the mixture?

0.3 0.2 0.5 1

The ratio of a mass concentration of species A to the total mass density of the mixture is known as

Mass density

Concentration

Mole fraction

Mass fraction

Which among the following is always true for mass transfer to occur?

Difference in concentration

Difference in pressure

Difference in temperature

Difference in chemical potential

A molecule in a mixture moves with a velocity of 0.03 m/s in the +x direction. The concentration of the particle is 0.5 mol/L. An observer is running in the -x direction with a velocity of 2 m/s. Calculate the value of molar flux (mol/m^2.s) relative to the observer.

0.015

15

1.015

1015

For a binary mixture of species A and B, the mass average velocity is defined as

2*p{a}*V{a} + p{b} V{b}/p

p{a}*V{a} + p{b} V{b}/p

p{a}*V{a}+ 2*p{b}*V{b}/p

p{a}*V{a} + p{b}*V{b}/(2*p)

For a binary mixture of species A and B, the molar average velocity is defined as

n{a}*V{a} + n{b}*V{b}

n{a}*V{a} + n{b}*V{b}/n

n{a}*V{a} + n{b}*V{b}/2*n

n{a}*V{a} + 2*n*{b}*V{b}/n

Which among the following can be the unit of flux?

kg*m^(-2)*s(-1)

kg*m^2*s^(-1)

kg*m^2*s^1

kg*m*s^2

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 10^5 N/m^2, find the mass fraction of oxygen.

0.133

0.233

0.333

0.433

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 10^5 N/m^2, find the molar fraction of nitrogen.

0.79

0.21

0.23

0.13

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 10^5 N/m^2, find the overall mass density.

4.156 kg/m^3

3.156 kg/m^3

2.156 kg/m^3

1.156 kg/m^3

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 10^5 N/m^2, find the molar concentration of oxygen.

8.42 * 10^(-1) kg mol/m^3

8.42 * 10^(-2) kg mol/m^3

8.42 * 10^(-3) kg mol/m^3

8.42 * 10^(-4) kg mol/m^3

A binary mixture of oxygen and nitrogen with partial pressures in the ratio 0.21 and 0.79 is contained in a vessel at 300 K. If the total pressure of the mixture is 10^5 N/m^2, find the average molecular weight of the mixture.

28.84

29.84

30.84

31.84

Under which of the following conditions are mass average velocity and molar average velocity equal?

In a very dilute solution

If molecular weights of all the species are equal

No condition; they are always different

In dilute solutions as well as in solutions whose components all have same molecular weights

Under which of the following conditions will mass transfer occur spontaneously? C and z are concentration and distance respectively.

dC/dz > 0

dC/dz < 0

dC/dz = 0

None of the above

Quiz/Test Summary
Title: Comparison of the Modes of Mass Transfer
Questions: 15
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