Chemical Equilibrium Contributions by: John L. Falconer & Will Medlin Department of Chemical and Biological Engineering University of Colorado Boulder, CO 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 K 1 = 1000 A + D  3 E K 2 = 78

For a gas phase reaction: A + B ↔ C + D What are the units of the equilibrium constant? A.bar 2 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.(x c  c )/(x A  A P B 2 ) B.P B -2 C.x c /(x A P B 2 ) D.f c /(f A P B 2 ) E.f c /(f A  B 2 P B 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 following reaction, what will happen to K a and to the equilibrium extent of reaction? A.Both with increase B.Both will decrease C.Both will stay the same D.K a will stay the same, extent of rxn will increase E.K a will increase, extent of rxn will stay the same C 2 H 4 (g) + ½ O 2 (g)  C 2 H 3 OH (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 C 4 H 8 C 4 H 6 + H 2

This reaction goes to equilibrium at 400°C in a closed container under two starting conditions: A)100 g Pd, 1 mol O 2 B)100 g Pd, 1 mol O 2, 1 g PdO The initial O 2 pressure is high enough to reach equilibrium. The Pd and PdO are in separte phases. The final O 2 pressure is _____________. A.higher for condition A B.higher for condition B C.the same for both conditions Pd O 2  PdO

A constant volume system contains CaO (s), CaCO 3(s), and CO 2(g) at chemical equilibrium at 850 K. When 0.1 mol N 2 is injected into the system at 850 K and constant pressure, what happens? Assume ideal gases. A.Some CaCO 3 decomposes B.All the CaCO 3 decomposes C.Some CO 2 reacts D.All the CO 2 reacts E.Nothing changes CaCO 3(s) CaO (s) N2N2 CaCO 3(s) CaO (s) + CO 2(g) CO 2

A piston-cylinder system contains CaO (s), CaCO 3(s), and CO 2(g) at chemical equilibrium at 850 K. When 0.1 mol N 2 is injected into the system at 850 K and constant pressure, what happens? A.Some CaCO 3 decomposes B.All the CaCO 3 decomposes C.Some CO 2 reacts D.All the CO 2 reacts E.Nothing changes CaCO 3(s) CaO (s) CO 2 N2N2 CaCO 3(s) CaO (s) + CO 2(g)

A constant volume system contains CaO (s), CaCO 3(s), CO 2(g), and N 2(g) at chemical equilibrium at 850 K. The N 2 is removed through a selective membrane at 850 K and constant pressure. Assume ideal gas. What happens? A.Some CaCO 3 decomposes B.All the CaCO 3 decomposes C.Some CO 2 reacts D.All the CO 2 reacts E.Nothing changes CO 2 CaCO 3(s) CaO (s) N2N2 CaCO 3(s) CaO (s) + CO 2(g)

A piston-cylinder system contains CaO (s), CaCO 3(s), CO 2(g), and N 2(g) at chemical equilibrium at 850 K. Some N 2 and CO 2 are removed at 850 K and constant pressure using a syringe. What happens? A.Some CaCO 3 decomposes B.All the CaCO 3 decomposes C.Some CO 2 reacts D.All the CO 2 reacts E.None of the above CaCO 3(s) CaO (s) CO 2 N 2 CaCO 3(s) CaO (s) + CO 2(g)

A piston-cylinder system contains CaO (s), CaCO 3(s), CO 2(g), and N 2(g) at chemical equilibrium at 850 K. All the N 2 is removed through a selective membrane at 850 K and constant pressure. What happens? A.Some CaCO 3 decomposes B.All the CaCO 3 decomposes C.Some CO 2 reacts D.All the CO 2 reacts E.Nothing changes CaCO 3(s) CaO (s) CO 2 N2N2 CaCO 3(s) CaO (s) + CO 2(g)

0.2 mol CaO, 10 mol CaCO 3, and 10 mol CO 2 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.CO 2 pressure almost doubles B.CaO and CO 2 react, so CO 2 pressure does not change C.System is at equilibrium, nothing changes D.All the CO 2 reacts CaCO 3(s) CaO (s) + CO 2(g) CaCO 3(s) CaO (s) CO 2

Staring at equilibrium, the piston is pushed down until the volume is half its original value while temperature is kept constant, what happens? A.CO 2 pressure is higher, amount of CaCO 3 is higher B.CaO and CO 2 react, so CO 2 pressure does not change C.System is at equilibrium, nothing changes D.All the CO 2 reacts CaCO 3(s) CaO (s) + CO 2(g) 1 mol CaCO 3(s) 10 mol CaO (s) 0.1 mol CO 2

Staring at equilibrium, the piston is pushed down until the volume is half its original value while temperature is kept constant, what happens? A.CO 2 pressure is higher, amount of CaCO 3 is higher B.CaO and CO 2 react, so CO 2 pressure does not change C.System is at equilibrium, nothing changes D.All the CO 2 reacts CaCO 3(s) CaO (s) + CO 2(g) 1 mol CaCO 3(s) 5 mol CaO (s) 5 mol CO 2

A piston-cylinder system contains C(s), CO 2, 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) + CO 2(g)  2 CO (g) C (s) CO 2 CO

A mixture of CO, O 2, and CO 2 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 CO 2(g) with MgO (s) is … A.Exothermic B.Endothermic C.Need more information MgCO 3(s) + CO 2 MgO (s) + CO 2 MgO (s) + CO 2 + MgCO 3(s) d log p CO2 (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 p CO2 = 10.4 atm. As the temperature further increases, p CO2 ___________. A.increases B.decreases C.remains the same MgO (s) + CO 2 (g)  MgCO 3(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: CH 4 + H 2 O  CO + 3 H 2 A.1 bar, 600 K B.1 bar, 1200 K C.100 bar, 600 K D.100 bar, 1200 K GAS ΔH f ° at 600 K ΔH f ° at 1300 K ΔG f ° at 600 K ΔG f ° at 1300 K CH H2OH2O CO CO kcal/mol

For an exothermic reaction in an adiabatic flow reactor, which statement is true? A.Decreasing the mass flow rate of an inert component in 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 adiabatic reactor. 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? CH 4 + H 2 O  CO + 3 H 2 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 + H 2 O  CO 2 + H 2