Engineering :: Mass Transfer

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Diffusion is a process of

A.	movement of particles from higher concentration to lower concentration	B.	movement of particles through a semipermeable membrane
C.	rarefaction of particles	D.	accumulation of particles on a solid surface

The diffusivity of a constituent A in solution B has the units.

A.	m/s	B.	m2/s
C.	m3/s	D.	kmol/(m2-s)

For steady-state molecular diffusion of gas A through non-diffusing B the ratio NA/(NA + NB) is

A.	0	B.	1
C.	?

For steady-state equimolal counterdiffusion of two gases A and A the ration NA/(NA + NB) is

A.	0	B.	1
D.	?

Methane is being cracked on a catalyst CH4?C + 2H2 under circumstances that CH4 (A) diffuses to the cracking surface and H2(B) diffuses back. At steady-state the ratio NA(NA + NB)is

A.	?	B.	1
C.	?	D.	2

The binary diffusivity in gases is dependent upon

A.	the temperature	B.	the pressure
C.	the nature of components	D.	all of the above

The binary diffusivity in gases varies almost as where T = absolute temperature of the system

A.	T	B.	T1/2
C.	T3/2	D.	T2

The binary diffusivity in gases varies

A.	directly as the pressure	B.	inversely as the pressure
C.	inversely as the square root of pressure	D.	directly as the square root of pressure

The binary diffusivity in gases at atmospheric conditions is of the order of

A.	10-1 cm2/sec	B.	10-5 cm2/sec
C.	105 cm2/sec	D.	10-7 cm2/sec

10.

The binary diffusivity in liquids is of the order of

A.	10-5 cm2/sec	B.	10-5 m2/sec
C.	10-5 mm2/sec	D.	10-5 ft2/sec