Question 1

For the following reaction at 25ºC, is 3 × 1024. 2SO2(g) + O2(g)   2SO3(g)
What is Kc at this temperature? (R = 0.08206 L • atm/K • mol)

Accepted Answer

A)  1 × 1023 
B)  1 × 1024 
C)  3 × 1024 
D)  6 × 1024 
E)  7 × 1025 
A)  1 × 1023 
B)  1 × 1024 
C)  3 × 1024 
D)  6 × 1024 
E)  7 × 1025

Question 2

Which statement is correct?

Accepted Answer

A)  If Q  K, then reactants must be converted to products. 
C)  If Q = K, then the system is at equilibrium. 
D)  If Q < K, then more reactants are produced. 
E)  None of the answers is correct. 
A)  If Q  K, then reactants must be converted to products. 
C)  If Q = K, then the system is at equilibrium. 
D)  If Q < K, then more reactants are produced. 
E)  None of the answers is correct.

Question 3

The equilibrium constants (expressed in atm) for the chemical reaction N2(g) + O2(g)   2NO(g) are KP = 1.1 × 10-3 and 3.6 × 10-3 at 2200 K and 2500 K, respectively.
Which statement is true?

Accepted Answer

A)  The reaction is exothermic, ΔHº p is less than Kc by a factor of (RT). 
D)  The total pressure at 2200 K is the same as at 2500 K. 
E)  Higher total pressure shifts the equilibrium to the left. 
A)  The reaction is exothermic, ΔHº p is less than Kc by a factor of (RT). 
D)  The total pressure at 2200 K is the same as at 2500 K. 
E)  Higher total pressure shifts the equilibrium to the left.

Question 4

For the reaction SO2(g) + NO2(g)   SO3(g) + NO(g), the equilibrium constant Kc is 18.0 at 1200ºC. If 1.0 mole of SO2 and 2.0 moles of NO2 are placed in a 20.0-L container, what concentration of SO3 will be present at equilibrium?

Accepted Answer

A)  0.048 mol/L 
B)  0.11 mol/L 
C)  0.95 mol/L 
D)  2.22 mol/L 
E)  18 mol/L 
A)  0.048 mol/L 
B)  0.11 mol/L 
C)  0.95 mol/L 
D)  2.22 mol/L 
E)  18 mol/L

Question 5

For any reaction, if ΔG° > 0, then K < 1.

Accepted Answer

A) True 
 B)False

Question 6

If the system 3H2(g) + N2(g)   2NH3(g) is at equilibrium and more N2 is added, a net reaction that consumes some of the added N2 will occur until a new equilibrium is reached.

Accepted Answer

A) True 
 B)False

Question 7

At 250ºC, the equilibrium constant, KP, for the reaction PCl5(g)   PCl3(g) + Cl2(g) is 1.80. Sufficient PCl5 is put into a reaction vessel to give an initial pressure of 2.74 atm at 250ºC. What is the partial pressure of PCl5 after the system has reached equilibrium.

Accepted Answer

A)  1.50 atm 
B)  1.24 atm 
C)  4.24 atm 
D)  0.94 atm 
E)  1.12 atm 
A)  1.50 atm 
B)  1.24 atm 
C)  4.24 atm 
D)  0.94 atm 
E)  1.12 atm

Question 8

When a reaction system reaches equilibrium, the forward and reverse reactions stop.

Accepted Answer

A) True 
 B)False

Question 9

When the concentrations of both the reactants and products remain constant because the forward and reverse reactions are occurring at the same rate then the system is ________.

Accepted Answer

The answer of When the concentrations of both the reactants...

Question 10

For the reaction HCONH2(g)   NH3(g) + CO(g), Kc = 4.84 at 400 K. If ΔH° for this reaction is 29 kJ/mol, find Kc at 500 K.

Accepted Answer

A)  5.8 
B)  0.17 
C)  27.5 
D)  0.88 
E)  10.3 
A)  5.8 
B)  0.17 
C)  27.5 
D)  0.88 
E)  10.3

Question 11

For ________-________ reactions KP = Kc(RT)Δn gas.

Accepted Answer

Question 12

For the following reaction at equilibrium, which one of the changes below would cause the equilibrium to shift to the left? 2NOBr(g)   2NO(g) + Br2(g), ΔHºrxn = 30 kJ/mol

Accepted Answer

A)  Increase the container volume 
B)  Remove some NO 
C)  Remove some Br2 
D)  Add more NOBr 
E)  Decrease the temperature 
A)  Increase the container volume 
B)  Remove some NO 
C)  Remove some Br2 
D)  Add more NOBr 
E)  Decrease the temperature

Question 13

Which is correct?

Accepted Answer

A)  If ΔG  K. 
B)  If ΔG o o  K. 
A)  If ΔG  K. 
B)  If ΔG o o  K.

Question 14

In the gas phase, formic acid forms a dimer, 2HCOOH(g)   (HCOOH)2(g). For this reaction, ΔH° = -60.1 kJ/mol and ΔG° = -13.9 kJ/mol at 25°C. Find the equilibrium constant (KP) for this reaction at 75 °C.

Accepted Answer

A)  8960 
B)  273 
C)  0.120 
D)  8.33 
E)  1.12 × 10-4 
A)  8960 
B)  273 
C)  0.120 
D)  8.33 
E)  1.12 × 10-4

Question 15

Which is the correct mass-action expression, Qc, for the following chemical reaction? Sn2+(aq) + ½ O2(g) + 3H2O(l)   SnO2(s) + 2H3O+(aq)

Accepted Answer

A)    
B)    
C)    
D)    
E)  None of these expressions is correct. 
A)    
B)    
C)    
D)    
E)  None of these expressions is correct.

Question 16

The equilibrium constant, Kc, for the reaction PCl3(g) + Cl2(g)   PCl5(g) is 49 at 230°C.
If 0.70 mol of PCl3 is added to 0.70 mol of Cl2 in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl3 when equilibrium has been established?

Accepted Answer

A)  0.049 M 
B)  0.11 M 
C)  0.35 M 
D)  0.59 M 
E)  0.83 M 
A)  0.049 M 
B)  0.11 M 
C)  0.35 M 
D)  0.59 M 
E)  0.83 M

Question 17

Suppose 4.2 mol of oxygen and 4.0 mol of NO are introduced to an evacuated 0.50-L reaction vessel. At a specific temperature, the equilibrium 2NO(g) + O2(g)   2NO2(g) is reached when [NO] = 1.6 M. Calculate Kc for the reaction at this temperature.

Accepted Answer

Question 18

Which equation is correct?

Accepted Answer

A)  ΔG = ΔG° - RT logKeq 
B)  ΔG° = - RT lnK 
C)  ΔG = RT lnQ 
D)  ΔG = -RT logQ 
E)  ΔG° = -RT logKeq 
A)  ΔG = ΔG° - RT logKeq 
B)  ΔG° = - RT lnK 
C)  ΔG = RT lnQ 
D)  ΔG = -RT logQ 
E)  ΔG° = -RT logKeq

Question 19

The equilibrium constant, KP, for the reaction H2(g) + I2(g)   2HI(g) is 55.2 at 425°C.
A rigid cylinder at that temperature contains 0.127 atm of hydrogen, 0.134 atm of iodine, and 1.055 atm of hydrogen iodide. Is the system at equilibrium?

Accepted Answer

A)  Yes. 
B)  No, the forward reaction must proceed to establish equilibrium. 
C)  No, the reverse reaction must proceed to establish equilibrium. 
D)  I need to know the volume of the container before deciding. 
E)  Need to know the starting pressures of all substances before deciding. 
A)  Yes. 
B)  No, the forward reaction must proceed to establish equilibrium. 
C)  No, the reverse reaction must proceed to establish equilibrium. 
D)  I need to know the volume of the container before deciding. 
E)  Need to know the starting pressures of all substances before deciding.

Question 20

For the endothermic reaction A2(g)   2A(g), a snapshot of an equilibrium mixture of A(g) and A2(g) at low temperature may look as follows. (Each circle represents 1.0 mol of A atoms, and the volume of the box is 1.0 L.)   If the system pressure is lowered, what might the new equilibrium system look like?

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Exam 15: Chemical Equilibrium

For the following reaction at 25ºC, is 3 × 1024. 2SO2(g) + O2(g) 2SO3(g) What is Kc at this temperature? (R = 0.08206 L • atm/K • mol)

Which statement is correct?

The equilibrium constants (expressed in atm) for the chemical reaction N2(g) + O2(g) 2NO(g) are KP = 1.1 × 10-3 and 3.6 × 10-3 at 2200 K and 2500 K, respectively. Which statement is true?

For the reaction SO2(g) + NO2(g) SO3(g) + NO(g), the equilibrium constant Kc is 18.0 at 1200ºC. If 1.0 mole of SO2 and 2.0 moles of NO2 are placed in a 20.0-L container, what concentration of SO3 will be present at equilibrium?

For any reaction, if ΔG° > 0, then K < 1.

If the system 3H2(g) + N2(g) 2NH3(g) is at equilibrium and more N2 is added, a net reaction that consumes some of the added N2 will occur until a new equilibrium is reached.

At 250ºC, the equilibrium constant, KP, for the reaction PCl5(g) PCl3(g) + Cl2(g) is 1.80. Sufficient PCl5 is put into a reaction vessel to give an initial pressure of 2.74 atm at 250ºC. What is the partial pressure of PCl5 after the system has reached equilibrium.

When a reaction system reaches equilibrium, the forward and reverse reactions stop.

When the concentrations of both the reactants and products remain constant because the forward and reverse reactions are occurring at the same rate then the system is ________.

For the reaction HCONH2(g) NH3(g) + CO(g), Kc = 4.84 at 400 K. If ΔH° for this reaction is 29 kJ/mol, find Kc at 500 K.

For ________-________ reactions KP = Kc(RT)Δn gas.

For the following reaction at equilibrium, which one of the changes below would cause the equilibrium to shift to the left? 2NOBr(g) 2NO(g) + Br2(g), ΔHºrxn = 30 kJ/mol

Which is correct?

In the gas phase, formic acid forms a dimer, 2HCOOH(g) (HCOOH)2(g). For this reaction, ΔH° = -60.1 kJ/mol and ΔG° = -13.9 kJ/mol at 25°C. Find the equilibrium constant (KP) for this reaction at 75 °C.

Which is the correct mass-action expression, Qc, for the following chemical reaction? Sn2+(aq) + ½ O2(g) + 3H2O(l) SnO2(s) + 2H3O+(aq)

The equilibrium constant, Kc, for the reaction PCl3(g) + Cl2(g) PCl5(g) is 49 at 230°C. If 0.70 mol of PCl3 is added to 0.70 mol of Cl2 in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl3 when equilibrium has been established?

Suppose 4.2 mol of oxygen and 4.0 mol of NO are introduced to an evacuated 0.50-L reaction vessel. At a specific temperature, the equilibrium 2NO(g) + O2(g) 2NO2(g) is reached when [NO] = 1.6 M. Calculate Kc for the reaction at this temperature.

Which equation is correct?

The equilibrium constant, KP, for the reaction H2(g) + I2(g) 2HI(g) is 55.2 at 425°C. A rigid cylinder at that temperature contains 0.127 atm of hydrogen, 0.134 atm of iodine, and 1.055 atm of hydrogen iodide. Is the system at equilibrium?

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For the following reaction at 25ºC, is 3 × 10²⁴. 2SO₂(g) + O₂(g) 2SO₃(g) What is K_c at this temperature? (R = 0.08206 L • atm/K • mol)

The equilibrium constants (expressed in atm) for the chemical reaction N₂(g) + O₂(g) 2NO(g) are K_P = 1.1 × 10^-3 and 3.6 × 10^-3 at 2200 K and 2500 K, respectively. Which statement is true?

For the reaction SO₂(g) + NO₂(g) SO₃(g) + NO(g), the equilibrium constant K_c is 18.0 at 1200ºC. If 1.0 mole of SO₂ and 2.0 moles of NO₂ are placed in a 20.0-L container, what concentration of SO₃ will be present at equilibrium?

If the system 3H₂(g) + N₂(g) 2NH₃(g) is at equilibrium and more N₂ is added, a net reaction that consumes some of the added N₂ will occur until a new equilibrium is reached.

At 250ºC, the equilibrium constant, K_P, for the reaction PCl₅(g) PCl₃(g) + Cl₂(g) is 1.80. Sufficient PCl₅ is put into a reaction vessel to give an initial pressure of 2.74 atm at 250ºC. What is the partial pressure of PCl₅ after the system has reached equilibrium.

For the reaction HCONH₂(g) NH₃(g) + CO(g), K_c = 4.84 at 400 K. If ΔH° for this reaction is 29 kJ/mol, find K_c at 500 K.

For - reactions K_P = K_c(RT)^Δⁿgas.

For the following reaction at equilibrium, which one of the changes below would cause the equilibrium to shift to the left? 2NOBr(g) 2NO(g) + Br₂(g), ΔHº_rxn= 30 kJ/mol

In the gas phase, formic acid forms a dimer, 2HCOOH(g) (HCOOH)₂(g). For this reaction, ΔH° = -60.1 kJ/mol and ΔG° = -13.9 kJ/mol at 25°C. Find the equilibrium constant (K_P) for this reaction at 75 °C.

Which is the correct mass-action expression, Q_c, for the following chemical reaction? Sn²⁺(aq) + ½ O₂(g) + 3H₂O(l) SnO₂(s) + 2H₃O⁺(aq)

The equilibrium constant, K_c, for the reaction PCl₃(g) + Cl₂(g) PCl₅(g) is 49 at 230°C. If 0.70 mol of PCl₃ is added to 0.70 mol of Cl₂ in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl₃ when equilibrium has been established?

Suppose 4.2 mol of oxygen and 4.0 mol of NO are introduced to an evacuated 0.50-L reaction vessel. At a specific temperature, the equilibrium 2NO(g) + O₂(g) 2NO₂(g) is reached when [NO] = 1.6 M. Calculate K_c for the reaction at this temperature.

The equilibrium constant, K_P, for the reaction H₂(g) + I₂(g) 2HI(g) is 55.2 at 425°C. A rigid cylinder at that temperature contains 0.127 atm of hydrogen, 0.134 atm of iodine, and 1.055 atm of hydrogen iodide. Is the system at equilibrium?