Q. For the equilibrium reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), what happens if SO3 is removed?
A.Equilibrium shifts to the right
B.Equilibrium shifts to the left
C.No change in equilibrium
D.Reaction stops
Solution
Removing SO3 decreases its concentration, causing the equilibrium to shift to the right to produce more SO3 and restore balance.
Correct Answer: A — Equilibrium shifts to the right
Q. For the equilibrium reaction A(g) + B(g) ⇌ C(g), if the reaction is endothermic, what is the effect of increasing pressure?
A.Shifts equilibrium to the right
B.Shifts equilibrium to the left
C.No effect on equilibrium
D.Increases the rate of the forward reaction
Solution
Increasing pressure favors the side with fewer moles of gas. If A and B have more moles than C, the equilibrium will shift to the left.
Correct Answer: B — Shifts equilibrium to the left
Q. For the equilibrium reaction CO(g) + 2H2(g) ⇌ CH3OH(g), what happens if the concentration of H2 is increased?
A.Equilibrium shifts to the right
B.Equilibrium shifts to the left
C.No change occurs
D.Reaction rate decreases
Solution
Increasing the concentration of H2 will shift the equilibrium to the right, favoring the production of CH3OH.
Correct Answer: A — Equilibrium shifts to the right
Q. For the reaction 2NO(g) + O2(g) ⇌ 2NO2(g), if the initial concentrations are [NO] = 0.5 M and [O2] = 0.2 M, what is the equilibrium concentration of NO2 if Kc = 10?
A.0.1 M
B.0.2 M
C.0.5 M
D.0.4 M
Solution
Using the expression Kc = [NO2]^2 / ([NO]^2[O2]), we find that at equilibrium [NO2] = 0.4 M.
Correct Answer: D — 0.4 M
Q. For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), what is the effect of increasing the pressure?
A.Shifts equilibrium to the left
B.Shifts equilibrium to the right
C.No effect on equilibrium
D.Increases the temperature
Solution
Increasing the pressure will shift the equilibrium to the right, favoring the production of SO3, as it has fewer moles of gas (3 moles to 2 moles).
Correct Answer: B — Shifts equilibrium to the right
Q. For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), what will happen if the temperature is decreased?
A.Equilibrium shifts to the right
B.Equilibrium shifts to the left
C.No change occurs
D.Reaction rate decreases
Solution
Decreasing the temperature of an exothermic reaction will shift the equilibrium to the right, favoring the formation of SO3.
Correct Answer: A — Equilibrium shifts to the right
Q. For the reaction 3H2(g) + N2(g) ⇌ 2NH3(g), if the temperature is decreased, what will be the effect on the equilibrium position?
A.Shift to the left
B.Shift to the right
C.No effect
D.Depends on pressure
Solution
If the reaction is exothermic, decreasing the temperature will shift the equilibrium to the right, favoring NH3 production.
Correct Answer: B — Shift to the right
Q. For the reaction A + B ⇌ C + D, if ΔH = -150 kJ and ΔS = -200 J/K, what is the temperature at which the reaction becomes non-spontaneous?
A.750 K
B.750 °C
C.300 K
D.150 K
Solution
At equilibrium, ΔG = 0; ΔG = ΔH - TΔS = 0; T = ΔH/ΔS = 150,000 J / 200 J/K = 750 K.
Correct Answer: A — 750 K
Q. For the reaction A(g) + B(g) ⇌ C(g), if the pressure is decreased, what will happen to the equilibrium?
A.Shift to the right
B.Shift to the left
C.No change
D.Reaction stops
Solution
Decreasing the pressure will shift the equilibrium to the side with more moles of gas, which in this case is the right side (C).
Correct Answer: A — Shift to the right
Q. For the reaction CO(g) + 2H2(g) ⇌ CH3OH(g), if the pressure is increased, what will be the effect on the equilibrium position?
A.Shift to the left
B.Shift to the right
C.No effect
D.Depends on temperature
Solution
Increasing pressure shifts the equilibrium towards the side with fewer moles of gas, which is the right side (1 mole of CH3OH).
Correct Answer: B — Shift to the right
Q. For the reaction H2(g) + I2(g) ⇌ 2HI(g), if the temperature is increased and Kc decreases, what does this indicate about the reaction?
A.Exothermic
B.Endothermic
C.Reversible
D.Irreversible
Solution
A decrease in Kc with an increase in temperature indicates that the reaction is exothermic.
Correct Answer: A — Exothermic
Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what happens if H2 is removed from the system?
A.Equilibrium shifts to the right
B.Equilibrium shifts to the left
C.No change occurs
D.NH3 concentration increases
Solution
Removing H2 decreases its concentration, causing the equilibrium to shift to the left to produce more reactants and restore balance.
Correct Answer: B — Equilibrium shifts to the left
Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what happens if the concentration of NH3 is decreased?
A.Equilibrium shifts to the right
B.Equilibrium shifts to the left
C.No change
D.Reaction stops
Solution
Decreasing the concentration of NH3 will shift the equilibrium to the right to produce more NH3, according to Le Chatelier's Principle.
Correct Answer: A — Equilibrium shifts to the right
Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what is the effect of decreasing the volume of the container?
A.Shifts equilibrium to the right
B.Shifts equilibrium to the left
C.No effect on equilibrium
D.Increases the concentration of NH3
Solution
Decreasing the volume increases the pressure, and according to Le Chatelier's Principle, the equilibrium will shift to the side with fewer moles of gas, which is to the right in this case.
Correct Answer: A — Shifts equilibrium to the right
Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what will happen if NH3 is removed from the system?
A.Shift to the right
B.Shift to the left
C.No change
D.Reaction stops
Solution
Removing NH3 will shift the equilibrium to the right to produce more NH3, in accordance with Le Chatelier's Principle.
Correct Answer: A — Shift to the right
Q. How does increasing temperature affect the enthalpy of a substance?
A.It decreases enthalpy.
B.It increases enthalpy.
C.It has no effect.
D.It depends on the substance.
Solution
Increasing temperature generally increases the enthalpy of a substance due to increased kinetic energy.
Correct Answer: B — It increases enthalpy.
Q. How does increasing temperature generally affect the enthalpy of a system?
A.It decreases the enthalpy
B.It has no effect on enthalpy
C.It increases the enthalpy
D.It depends on the type of reaction
Solution
Increasing temperature typically increases the enthalpy of a system due to the increased kinetic energy of the molecules.
Correct Answer: C — It increases the enthalpy
Q. How does increasing the temperature affect the equilibrium constant (K) of an endothermic reaction?
A.K decreases
B.K increases
C.K remains constant
D.K becomes zero
Solution
For an endothermic reaction, increasing the temperature increases the equilibrium constant (K) as the reaction favors the formation of products.
Correct Answer: B — K increases
Q. How does the addition of an inert gas at constant volume affect the equilibrium of a reaction?
A.Shifts equilibrium to the right
B.Shifts equilibrium to the left
C.No effect on equilibrium
D.Increases the reaction rate
Solution
Adding an inert gas at constant volume does not change the partial pressures of the reactants or products, thus having no effect on the equilibrium position.
Correct Answer: C — No effect on equilibrium
Q. How many grams of sodium chloride are needed to prepare 0.5 L of a 0.2 M solution?
A.5.84 g
B.11.68 g
C.2.92 g
D.0.58 g
Solution
Molar mass of NaCl = 58.44 g/mol. Moles needed = 0.2 M * 0.5 L = 0.1 moles. Mass = moles * molar mass = 0.1 * 58.44 g = 5.844 g.
Correct Answer: B — 11.68 g
Q. How many moles of potassium hydroxide are needed to neutralize 0.1 moles of hydrochloric acid?
A.0.05
B.0.1
C.0.2
D.0.3
Solution
The reaction between KOH and HCl is 1:1. Therefore, 0.1 moles of HCl will require 0.1 moles of KOH.
Correct Answer: B — 0.1
Q. How many stereoisomers can 2,3-dimethylbutane have?
A.2
B.4
C.8
D.16
Solution
2,3-dimethylbutane has no chiral centers, so it has only 1 stereoisomer.
Correct Answer: A — 2
Q. How many stereoisomers does 1,2-dichloropropane have?
A.1
B.2
C.3
D.4
Solution
1,2-dichloropropane has one chiral center, leading to 2 stereoisomers.
Correct Answer: B — 2
Q. If 25 mL of 0.5 M acetic acid is mixed with 25 mL of 0.5 M sodium acetate, what is the resulting pH of the buffer solution?
A.4.76
B.5.00
C.5.76
D.6.00
Solution
Using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). pKa of acetic acid is approximately 4.76. Since [A-] = [HA], pH = 4.76.
Correct Answer: A — 4.76
Q. If 50 mL of 0.1 M sulfuric acid is neutralized by sodium hydroxide, how many moles of NaOH are required?
A.0.005
B.0.01
C.0.02
D.0.03
Solution
H2SO4 dissociates to give 2 H+ ions. Moles of H2SO4 = 0.1 M * 0.050 L = 0.005 moles. Therefore, moles of NaOH required = 0.005 moles * 2 = 0.01 moles.
Correct Answer: B — 0.01
Q. If a compound has a molar absorptivity of 200 L/(mol·cm) and a concentration of 0.01 mol/L, what is the absorbance at a path length of 1 cm?
A.0.2
B.2
C.20
D.0.02
Solution
Using Beer-Lambert Law (A = εlc), A = 200 L/(mol·cm) * 0.01 mol/L * 1 cm = 2.
Correct Answer: A — 0.2
Q. If a sample absorbs light at 250 nm with an absorbance of 0.5, what is the transmittance?
A.50%
B.25%
C.75%
D.100%
Solution
Transmittance (T) can be calculated using the formula T = 10^(-A). For A = 0.5, T = 10^(-0.5) = 0.316, which is approximately 50%.
Correct Answer: A — 50%
Q. If a solution has a concentration of 0.1 M and a path length of 1 cm, what is the absorbance if ε = 200 L/(mol·cm)?
A.20
B.0.2
C.2
D.200
Solution
Using Beer-Lambert Law, A = εcl = 200 L/(mol·cm) * 0.1 mol/L * 1 cm = 20.
Correct Answer: C — 2
Q. If a system at equilibrium is disturbed by adding a product, what is the expected outcome?
A.Shifts to the right
B.Shifts to the left
C.No effect
D.Increases the reaction rate
Solution
Adding a product increases its concentration, causing the equilibrium to shift to the left to favor the formation of reactants and restore balance.
Correct Answer: B — Shifts to the left
Q. If the enthalpy change (ΔH) for a reaction is -150 kJ and the reaction occurs at constant pressure, how much heat is released when 3 moles of reactants are consumed?
A.50 kJ
B.150 kJ
C.450 kJ
D.300 kJ
Solution
Heat released = ΔH * n = -150 kJ * 3 mol = -450 kJ.
