Q. In a reaction, if the concentration of reactant A is halved, and the rate constant remains the same, how does the rate change for a first-order reaction? (2021)
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
Solution
For a first-order reaction, if [A] is halved, the rate also halves.
Q. In a reaction, if the concentration of reactant A is halved, and the rate of reaction decreases to one-fourth, what is the order of the reaction? (2020)
A.
Zero
B.
First
C.
Second
D.
Third
Solution
If the rate decreases to one-fourth when concentration is halved, the reaction is second-order.
Q. In a reversible reaction at equilibrium, if the temperature is increased, what will happen to the equilibrium position if the reaction is exothermic? (2023)
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase the rate of reaction
Solution
For an exothermic reaction, increasing the temperature shifts the equilibrium position to the left, favoring the reactants, as the system tries to absorb the added heat.
Q. In a reversible reaction at equilibrium, which of the following statements is true?
A.
The rate of the forward reaction is equal to the rate of the reverse reaction.
B.
The concentration of reactants is greater than products.
C.
The reaction has stopped completely.
D.
The temperature remains constant.
Solution
At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, which means the concentrations of reactants and products remain constant over time.
Correct Answer:
A
— The rate of the forward reaction is equal to the rate of the reverse reaction.
Q. In a reversible reaction, if the concentration of products increases, what happens to the rate of the forward reaction? (2021)
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
Solution
According to Le Chatelier's principle, if the concentration of products increases, the system will shift to the left, decreasing the rate of the forward reaction.
Q. In a reversible reaction, if the concentration of products is increased, what will happen to the equilibrium position? (2021)
A.
Shift to the left
B.
Shift to the right
C.
No change
D.
Depends on temperature
Solution
According to Le Chatelier's principle, increasing the concentration of products will shift the equilibrium position to the left to counteract the change.
Q. In a reversible reaction, if the concentration of reactants is increased, what will happen to the position of equilibrium? (2021)
A.
It will shift to the right
B.
It will shift to the left
C.
It will remain unchanged
D.
It will shift to the center
Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right to favor the formation of products.
Q. In a reversible reaction, if the concentration of reactants is increased, what will happen to the equilibrium position? (2021)
A.
It will shift to the right
B.
It will shift to the left
C.
It will remain unchanged
D.
It will shift to the center
Solution
According to Le Chatelier's principle, if the concentration of reactants is increased, the equilibrium will shift to the right to favor the formation of products.
Q. In a reversible reaction, if the concentration of the reactants is increased, what will happen to the position of equilibrium? (2023)
A.
It will shift to the right
B.
It will shift to the left
C.
It will remain unchanged
D.
It will shift to the center
Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right, favoring the formation of products.
Q. In a second-order reaction, if the initial concentration is 0.1 M and the rate constant is 0.05 M⁻¹s⁻¹, what is the time taken to reach half the initial concentration? (2020)
A.
10 s
B.
20 s
C.
5 s
D.
15 s
Solution
For a second-order reaction, t₁/₂ = 1 / (k[A₀]) = 1 / (0.05 * 0.1) = 200 s.
