Equilibrium
Q. A ladder leans against a wall and is in equilibrium. What forces are acting on the ladder?
A.
Weight, normal force from the ground, and friction
B.
Only weight and normal force
C.
Only weight and friction
D.
Only normal force and friction
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Solution
The ladder experiences weight, a normal force from the ground, and friction at the base.
Correct Answer: A — Weight, normal force from the ground, and friction
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Q. A particle is in equilibrium under the action of three forces. If two forces are known, how can the third force be determined?
A.
By vector addition of the first two forces
B.
By subtracting the first two forces
C.
By multiplying the first two forces
D.
By taking the average of the first two forces
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Solution
The third force can be determined by vector addition of the first two forces to ensure the net force is zero.
Correct Answer: A — By vector addition of the first two forces
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Q. Calculate the pH of a 0.1 M acetic acid solution (Ka = 1.8 x 10^-5).
A.
2.87
B.
3.87
C.
4.87
D.
5.87
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Solution
Using the formula for weak acids, pH = 0.5(pKa - log[C]), where pKa = -log(1.8 x 10^-5) ≈ 4.74. Thus, pH = 0.5(4.74 - log(0.1)) = 3.87.
Correct Answer: B — 3.87
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Q. Calculate the pH of a buffer solution containing 0.1 M acetic acid and 0.1 M sodium acetate.
A.
4.76
B.
5.76
C.
6.76
D.
7.76
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Solution
Using Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]); pKa of acetic acid = 4.76, so pH = 4.76 + log(1) = 4.76
Correct Answer: B — 5.76
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Q. For the equilibrium 2A(g) ⇌ B(g) + C(g), how many moles of gas are on the reactant side?
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Solution
There are 2 moles of gas on the reactant side (2A).
Correct Answer: B — 2
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Q. For the equilibrium 2A(g) ⇌ B(g) + C(g), if the concentration of B is increased, what will happen to the concentration of A?
A.
Increase
B.
Decrease
C.
Remain the same
D.
Cannot be determined
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Solution
According to Le Chatelier's principle, increasing the concentration of B will shift the equilibrium to the left, resulting in a decrease in the concentration of A.
Correct Answer: B — Decrease
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Q. For the equilibrium 2A(g) ⇌ B(g) + C(g), if the volume of the container is decreased, what will happen?
A.
Shift to the left
B.
Shift to the right
C.
No change
D.
Depends on the temperature
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Solution
Decreasing the volume increases the pressure, and the equilibrium will shift towards the side with fewer moles of gas, which is the right side in this case.
Correct Answer: B — Shift to the right
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Q. For the equilibrium 2A(g) ⇌ B(g) + C(g), if the volume of the container is doubled, what will happen to the equilibrium position?
A.
Shift to the left
B.
Shift to the right
C.
No change
D.
Depends on the temperature
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Solution
Doubling the volume decreases the pressure, which shifts the equilibrium towards the side with more moles of gas, in this case, the right side.
Correct Answer: B — Shift to the right
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Q. For the equilibrium reaction 4HCl(g) ⇌ 2H2(g) + 2Cl2(g), how will the equilibrium shift if the temperature is decreased?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in pressure
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Solution
Decreasing the temperature for an endothermic reaction will shift the equilibrium to the left, favoring the formation of HCl.
Correct Answer: B — Shift to the left
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Q. For the equilibrium reaction CO(g) + 2H2(g) ⇌ CH3OH(g), if the temperature is decreased, what will be the effect?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in pressure
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Solution
Decreasing the temperature for an exothermic reaction will shift the equilibrium to the right, favoring the formation of products.
Correct Answer: A — Shift to the right
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Q. For the equilibrium reaction N2(g) + 3H2(g) ⇌ 2NH3(g), how will the equilibrium shift if H2 is added?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in temperature
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Solution
Adding H2 will shift the equilibrium to the right to produce more NH3.
Correct Answer: A — Shift to the right
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Q. For the equilibrium reaction N2(g) + 3H2(g) ⇌ 2NH3(g), if the pressure is increased, what will be the effect on the equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in temperature
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Solution
Increasing the pressure will shift the equilibrium to the right, favoring the formation of NH3, which has fewer moles of gas.
Correct Answer: A — Shift to the right
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Q. For the equilibrium reaction: H2(g) + I2(g) ⇌ 2HI(g), what is the effect of adding more HI?
A.
Shifts to the right
B.
Shifts to the left
C.
No change
D.
Increases the rate of reaction
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Solution
Adding more HI increases the concentration of products, which shifts the equilibrium to the left to form more reactants.
Correct Answer: B — Shifts to the left
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Q. For the equilibrium reaction: H2(g) + I2(g) ⇌ 2HI(g), what is the effect of adding more I2?
A.
Equilibrium shifts to the right
B.
Equilibrium shifts to the left
C.
No effect
D.
Equilibrium constant changes
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Solution
Adding more I2 increases its concentration, which shifts the equilibrium to the right to produce more HI.
Correct Answer: A — Equilibrium shifts to the right
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Q. For the reaction 2A(g) ⇌ B(g) + C(g), if the concentration of B is increased, what will happen to the equilibrium?
A.
Shift to the left
B.
Shift to the right
C.
No shift
D.
Depends on temperature
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Solution
Increasing the concentration of a product shifts the equilibrium to the left to counteract the change.
Correct Answer: A — Shift to the left
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Q. For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), if the concentration of SO2 is doubled, what happens to the equilibrium constant?
A.
It doubles
B.
It remains the same
C.
It halves
D.
It quadruples
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Solution
The equilibrium constant Kc is only affected by temperature, not by changes in concentration.
Correct Answer: B — It remains the same
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Q. For the reaction 4H2(g) + 2O2(g) ⇌ 4H2O(g), what is the change in Gibbs free energy at equilibrium?
A.
Positive
B.
Negative
C.
Zero
D.
Depends on temperature
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Solution
At equilibrium, the change in Gibbs free energy (ΔG) is zero.
Correct Answer: C — Zero
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Q. For the reaction 4HCl(g) ⇌ 2H2(g) + Cl2(g), what is the effect of adding HCl on the equilibrium?
A.
Shift to the left
B.
Shift to the right
C.
No effect
D.
Depends on the temperature
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Solution
Adding more HCl will increase the concentration of reactants, causing the equilibrium to shift to the left to consume the added HCl.
Correct Answer: A — Shift to the left
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Q. For the reaction A + B ⇌ C + D, if the concentration of C is decreased, what will be the effect on the equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in temperature
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Solution
Decreasing the concentration of C will shift the equilibrium to the right to produce more C and D.
Correct Answer: A — Shift to the right
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Q. For the reaction A(g) ⇌ B(g), if the concentration of A is increased, what will happen to the concentration of B at equilibrium?
A.
Increase
B.
Decrease
C.
Remain the same
D.
Cannot be determined
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Solution
Increasing the concentration of A will shift the equilibrium to the right, resulting in an increase in the concentration of B.
Correct Answer: A — Increase
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Q. For the reaction CO(g) + 2H2(g) ⇌ CH3OH(g), what is the effect of increasing the concentration of H2?
A.
Shifts equilibrium to the right
B.
Shifts equilibrium to the left
C.
No effect
D.
Increases the rate of reaction
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Solution
Increasing the concentration of H2 will shift the equilibrium to the right to produce more CH3OH, according to Le Chatelier's principle.
Correct Answer: A — Shifts equilibrium to the right
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Q. For the reaction CO(g) + 2H2(g) ⇌ CH3OH(g), what will happen if H2 is removed from the system?
A.
Shifts to the right
B.
Shifts to the left
C.
No change
D.
Increases the rate of reaction
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Solution
Removing a reactant (H2) will shift the equilibrium position to the left to produce more reactants.
Correct Answer: B — Shifts to the left
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Q. For the reaction CO(g) + 2H2(g) ⇌ CH3OH(g), what will happen if the concentration of H2 is increased?
A.
Equilibrium shifts to the left
B.
Equilibrium shifts to the right
C.
No change
D.
Rate of reaction decreases
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Solution
Increasing the concentration of H2 will shift the equilibrium to the right to produce more CH3OH, according to Le Chatelier's principle.
Correct Answer: B — Equilibrium shifts to the right
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Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), if the concentration of NH3 is increased, what will happen to the equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase the rate of reaction
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Solution
According to Le Chatelier's principle, increasing the concentration of a product (NH3) will shift the equilibrium to the left to counteract the change.
Correct Answer: B — Shift to the left
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Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what happens if the volume of the container is decreased?
A.
Equilibrium shifts to the left
B.
Equilibrium shifts to the right
C.
No change in equilibrium
D.
Equilibrium constant changes
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Solution
Decreasing the volume increases the pressure, and according to Le Chatelier's principle, the equilibrium will shift towards the side with fewer moles of gas, which is the right side in this case.
Correct Answer: B — Equilibrium shifts to the right
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Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what happens to the equilibrium constant if the temperature is increased?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Depends on the pressure
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Solution
For exothermic reactions, increasing the temperature shifts the equilibrium to the left, thus decreasing the equilibrium constant.
Correct Answer: B — Decreases
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Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what happens to the equilibrium position if the pressure is increased?
A.
Shifts to the left
B.
Shifts to the right
C.
No change
D.
Depends on temperature
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Solution
Increasing the pressure shifts the equilibrium towards the side with fewer moles of gas. In this case, the right side has 2 moles of NH3 compared to 4 moles of reactants.
Correct Answer: B — Shifts to the right
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Q. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what happens to the equilibrium position if the volume of the container is decreased?
A.
Equilibrium shifts to the left
B.
Equilibrium shifts to the right
C.
No change in equilibrium
D.
Equilibrium shifts in both directions
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Solution
According to Le Chatelier's principle, decreasing the volume increases the pressure, and the equilibrium will shift towards the side with fewer moles of gas, which is the right side (2 moles of NH3).
Correct Answer: B — Equilibrium shifts to the right
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Q. For the reaction: 3A(g) ⇌ 2B(g) + C(g), what is the expression for Kp?
A.
(P_B^2 * P_C) / (P_A^3)
B.
(P_A^3) / (P_B^2 * P_C)
C.
(P_C) / (P_A^3)
D.
(P_B^2) / (P_A^3)
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Solution
The equilibrium constant Kp is expressed as Kp = (P_B^2 * P_C) / (P_A^3).
Correct Answer: A — (P_B^2 * P_C) / (P_A^3)
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Q. For the reaction: A(g) ⇌ B(g) + C(g), if the concentration of A is increased, what will happen to the equilibrium position?
A.
Shift to the left
B.
Shift to the right
C.
No change
D.
Depends on temperature
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Solution
According to Le Chatelier's principle, increasing the concentration of a reactant will shift the equilibrium to the right.
Correct Answer: B — Shift to the right
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