Effectiveness factor (E) of a catalyst pellet is defined as, E = (actual rate within pore of catalyst/rate if notsnowed by pore diffusion) Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus)

For the reaction, A = X + Y, the respective concentrations are C_A, C_X and C_Y. The forward reaction rate constant is kf and the backward reaction rate constant is kb. Choose the correct statement from the following:
P. At equilibrium, kf C_A > k_B CxCy
Q. If the reaction is irreversible than, kb C_XC_Y = 0
R. The backward reaction rate will essentially be first order, if the forward reaction rate is first order.
S. Activation energy for the first order forward reaction will be independent of temperature.

A

P, Q

B

Q, R

C

R, S

D

Q, S

A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than at the external surface, the process is limited by

A

Diffusion within the pellet

B

Reaction

C

External mass transfer

D

None of the above

A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A is rate controlling. The effectiveness factor of the catalyst is reported as $$\frac{7}{8}$$. Which of the following statement is true?

A

Inner catalyst core of radius $$\frac{{\text{R}}}{8}$$ does not participate in reaction

B

Inner catalyst core of radius $$\frac{{\text{R}}}{2}$$ does not participate in reaction

C

Inner catalyst core of radius $$\frac{{7{\text{R}}}}{8}$$ does not participate in reaction

D

Effectiveness factor for a zero order reaction can not be $$\frac{7}{8}$$ as it must always be 1

For a first order chemical reaction in a porous catalyst, the Thiele modulus is 10. The effectiveness factor is approximately equal to

A

1

B

0.5

C

0.1

D

0

The effectiveness factor for large value of Thiele modulus $${\text{L}}\sqrt {{\text{K}}/{{\text{D}}_1}} $$ of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D₁ = diffusion co-efficient, cm²/second)

A

$${\text{L}}\sqrt {{\text{K}}/{{\text{D}}_1}} $$

B

$$\frac{1}{{{\text{L}}\sqrt {{\text{K}}/{{\text{D}}_1}} }}$$

C

1

D

$$\infty $$

If Thiele modulus is __________ , then the pore diffusion resistance in a catalyst may be considered as negligible.

A

0

B

∞

C

> 0.5

For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the

A

Catalyst size is reduced or the catalyst diffusivity is reduced

B

Catalyst size is reduced or the catalyst diffusivity is increased

C

Catalyst size is increased or the catalyst diffusivity is reduced

D

Catalyst size is increased or the catalyst diffusivity is increased

Effectiveness factor of a catalyst pellet is a measure of the __________ resistance.

A

Pore diffusion

B

Gas film

C

Chemical reaction

D

None of these

A solid-oxide fuel cell is fed with carbon monoxide and reacts with air to produce CO2. This reaction will produce 2 electrons which are used to power an electric circuit external to the fuel cell. The reaction equation is shown below: 2CO(g) + O2(g) -> 2CO2(g) ΔHr° = -565.96 kJ/mol This reaction does not occur for other types of fuel cells which use a catalyst, such as polymerelectrolyte membrane or phosphoric-acid fuel cells. The presence of carbon monoxide on the anode side of these types of fuel cells will cause catalyst poisoning, reducing the efficiency and voltage of the fuel cell. Determine the rate of enthalpy change for a carbon dioxide production rate of 208 mol/hr. The extent of the reaction occurring in the fuel cell can be obtained by the following equation: where:

A

-16.35 kW

B

-15.35 kW

C

-16.45 kW

D

-15.45 kW

Consider the following statements regarding the importance of diffusion and choose the correct answer:
1. The exchange of gases takes place by the principle of dependent diffusion
2. The process of diffusion is involved in transpiration of water vapours
3. The ions are absorbed by the simple diffusion during passive salt uptake
4. Diffusion is an effective means of transport of substances over a very short distance and helps in the translocation of food materials

A

1, 3 and 4 are true

B

1 and 4 are true

C

1, 2 and 3 are true

D

2, 3 and 4 are true

Effectiveness factor (E) of a catalyst pellet is defined as, E = (actual rate within pore of catalyst/rate if notsnowed by pore diffusion) Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus)

Related Questions