chemical equilibrium contributions by: john l. falconer & will medlin department of chemical and...

Chemical EquilibriumContributions by:

John L. Falconer & Will MedlinDepartment of Chemical and Biological Engineering

University of ColoradoBoulder, CO 80309-0424

Supported by the National Science Foundation

Consider the two reaction and their equilibrium constants:

Which conclusion is incorrect?

A. Reaction 1 reaches equilibrium first

B. Reaction 2 reaches equilibrium first

C. Reaction 2 has a higher conversion at equilibrium

D. None of these

A + B C K1 = 1000

A + D 3 E K2 = 78

For a gas phase reaction:

A + B ↔ C + DWhat are the units of the equilibrium constant?

A. bar2

B. bar

C. bar -1

D. It is dimensionless

For the gas phase reaction:

The equilibrium constant is 10 at 2 atm.What is the equilibrium constant at 10 atm?

A. 250

B. 10

C. 0.40

D. 50

A 3 B

What is the expression for the equilibrium constant for the following reaction?

A(l) and C(l) are immiscible, B is an ideal gas.

A. (xcc)/(xAAPB2)

B. PB-2

C. xc/(xAPB2)

D. fc/(fAPB2)

E. fc/(fAB2PB

2)

A(l) + 2 B(g) C(l)

For which reaction would the equilibrium conversion increase if inert gases were added to a flow system at constant total pressure?

A. 2A B

B. B 2 A

C. A B

D. None of these

As the total pressure is increased for the followingreaction, what will happen to Ka and to the equilibrium

extent of reaction?

A. Both with increase

B. Both will decrease

C. Both will stay the same

D. Ka will stay the same, extent of rxn will increase

E. Ka will increase, extent of rxn will stay the same

C2H4 (g) + ½ O2 (g) C2H3OH (l)

Given the following reaction:

If steam is added to the feed and everything else kept the same, the equilibrium conversion ___________.

A. increases

B. decreases

C. remains the same

C4H8 C4H6 + H2

This reaction goes to equilibrium at 400°C in a closed container under two starting conditions:

A) 100 g Pd, 1 mol O2

B) 100 g Pd, 1 mol O2, 1 g PdO

The initial O2 pressure is high enough to reach

equilibrium. The Pd and PdO are in separte phases. The final O2 pressure is _____________.

A. higher for condition A

B. higher for condition B

C. the same for both conditions

Pd + 0.5 O2 PdO

A constant volume system contains CaO(s), CaCO3(s),

and CO2(g) at chemical equilibrium at 850 K. When 0.1

mol N2 is injected into the system at 850 K and

constant pressure, what happens? Assume ideal gases.

A. Some CaCO3 decomposes

B. All the CaCO3 decomposes

C. Some CO2 reacts

D. All the CO2 reacts

E. Nothing changesCaCO3(s)

CaO(s)

N2

CaCO3(s) CaO(s) + CO2(g)

CO2

A piston-cylinder system contains CaO(s), CaCO3(s),

and CO2(g) at chemical equilibrium at 850 K. When 0.1

mol N2 is injected into the system at 850 K and

constant pressure, what happens?



C. Some CO2 reacts


E. Nothing changesCaCO3(s)

CaO(s)

CO2

N2


A constant volume system contains CaO(s), CaCO3(s),

CO2(g), and N2(g) at chemical equilibrium at 850 K. The

N2 is removed through a selective membrane at 850 K

and constant pressure. Assume ideal gas. What happens?



C. Some CO2 reacts


E. Nothing changes

CO2

CaCO3(s)

CaO(s)

N2



CO2(g), and N2(g) at chemical equilibrium at 850 K.

Some N2 and CO2 are removed at 850 K and constant

pressure using a syringe. What happens?



C. Some CO2 reacts


E. None of the aboveCaCO3(s)

CaO(s)

CO2

CO2

N2



CO2(g), and N2(g) at chemical equilibrium at 850 K. All the

N2 is removed through a selective membrane at 850 K

and constant pressure. What happens?



C. Some CO2 reacts


E. Nothing changes CaCO3(s)

CaO(s)

CO2N2


0.2 mol CaO, 10 mol CaCO3, and 10 mol CO2 are in a

piston-cylinder system. Starting at equilibrium, the piston is pushed down at constant temperature until the volume is half its original value. What happens?

A. CO2 pressure almost doubles

B. CaO and CO2 react, so CO2 pressure does not change

C. System is at equilibrium, nothing changes



CaCO3(s)

CaO(s)

CO2

Staring at equilibrium, the piston is pushed down until the volume is half its original value while temperature is kept constant, what happens?

A. CO2 pressure is higher, amount of CaCO3 is higher





1 molCaCO3(s)

10 molCaO(s)

0.1 molCO2

Staring at equilibrium, the piston is pushed down until the volume is half its original value while temperature is kept constant, what happens?

A. CO2 pressure is higher, amount of CaCO3 is higher





1 molCaCO3(s)

5 molCaO(s)

5 molCO2

A piston-cylinder system contains C(s), CO2, and CO

in equilibrium.

1 kg of carbon is added to the system and it returns to equilibrium at the same temperature and pressure. The solid occupies an insignificant volume. The CO pressure ____________.

A. increases

B. decreases

C. remains the same

C(s) + CO2(g) 2 CO(g)

C(s)

CO2

CO

A mixture of CO, O2, and CO2 gases have been sealed

in a container for 3 weeks at 25°C. The composition has not changed measurably. What can you conclude about this system?

A. The gases are at equilibrium

B. The kinetics are very slow

C. There is no leak in the container

D. All of the above

The reaction of CO2(g) with MgO(s) is …

A. Exothermic

B. Endothermic

C. Need more information

MgCO3(s) + CO2

MgO(s) + CO2

MgO

(s) + CO2 + M

gCO3(s)

d

log pCO2

(atm)

1/T

The exothermic reaction:

takes place in a fixed-volume, sealed container. The two solids are in separate phases. At 500 K, equilibrium is obtained when pCO2 = 10.4 atm. As the

temperature further increases, pCO2 ___________.

A. increases

B. decreases

C. remains the same

MgO(s) + CO2 (g) MgCO3(s)

For an exothermic reaction, which is the correct plot of equilibrium conversion (fraction of reactant reacted) vs. temperature ?

A B

DC

T

X

T

X

T

X

T

X

What conditions would you carry out this gas-phase reaction:

CH4 + H2O CO + 3 H2

A. 1 bar, 600 K

B. 1 bar, 1200 K

C. 100 bar, 600 K

D. 100 bar, 1200 K

GASΔHf° at 600 K

ΔHf° at1300 K

ΔGf° at600 K

ΔGf° at1300 K

CH4 -20 -22 -5.5 12

H2O -58 -60 -51 -42

CO -26 -27 -39 -54

CO2 -94 -94 -94 -97

kcal/mol

For an exothermic reaction in an adiabatic flow reactor, which statement is true?

A. Decreasing the mass flow rate of an inert componentin the feed increases equilibrium conversion.

B. The temperature will initially go up, but then decrease as equilibrium is approached.

C. Increasing the inlet temperature increases the equilibrium conversion.

D. None of the above

The equilibrium extent of reaction for an exothermic reaction will be higher for _______________

A. an adiabatic reactor

B. an isothermal reactor

C. neither adiabatic nor isothermal

An endothermic reaction takes place in an adiabaticreactor. The reactor is large enough so that conversion is complete. If the inlet flow rate is decreased by a factor of two, the exit temperature ________.

A. increases

B. decreases

C. remains the same

Consider the endothermic steam reforming of methane:

Which trend describes the extent of equilibrium conversion as a function of temperature?

CH4 + H2O CO + 3 H2

T

ξ

equil.C

B

A

The starting conditions for this reaction are indicated:

A(g) + B(g) C(s) 3 bar 3 bar x mol

The reaction proceeds to the right. Which will have the lower pressure of A at equilibrium?

A. x = 0.01 mol

B. x = 2 mol

C. Same pressure of A for both

The exothermic water‐gas shift reaction is often conducted downstream of the reforming reactor to generate excess hydrogen and to remove CO. The reaction is conducted in a sequence of two reactors. What is the appropriate sequence?

A. A high T reactor followed by a low T reactor

B. A low T reactor followed by a high T reactor

C. A high P reactor followed by a low P reactor

D. A low P reactor followed by a high P reactor

CO + H2O CO2 + H2

chemical equilibrium contributions by: john l. falconer & will medlin department of chemical and...

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