Q. In a first-order reaction, if the half-life is 10 minutes, what will be the concentration after 30 minutes if the initial concentration is 1 M?
A.
0.125 M
B.
0.5 M
C.
0.75 M
D.
0.25 M
Solution
For a first-order reaction, the concentration after n half-lives is given by [A] = [A]0 * (1/2)^n. After 30 minutes (3 half-lives), [A] = 1 M * (1/2)^3 = 0.125 M.
Q. In a first-order reaction, if the half-life is 10 minutes, what will be the half-life after doubling the temperature?
A.
5 minutes
B.
10 minutes
C.
20 minutes
D.
It cannot be determined
Solution
For first-order reactions, the half-life is independent of concentration but depends on the rate constant, which increases with temperature. Typically, the half-life will decrease, but the exact value requires the Arrhenius equation.
Q. In a qualitative analysis using paper chromatography, which factor primarily affects the separation of ions?
A.
Temperature
B.
Solvent polarity
C.
pH of the solution
D.
Ion concentration
Solution
The solvent polarity is the primary factor affecting the separation of ions in paper chromatography, as it influences the interaction between the stationary phase and the ions.
Q. In a qualitative analysis using paper chromatography, which factor primarily affects the Rf value of a substance?
A.
Solvent polarity
B.
Temperature
C.
pH of the solution
D.
Molecular weight
Solution
The Rf value is primarily affected by the polarity of the solvent used in paper chromatography, as it influences the interaction between the stationary phase and the analyte.
Q. In a reaction A → B, if the rate of formation of B is 0.5 M/s, what is the rate of disappearance of A?
A.
0.5 M/s
B.
1.0 M/s
C.
0.25 M/s
D.
0.75 M/s
Solution
For a 1:1 stoichiometry, the rate of disappearance of A is equal to the rate of formation of B. Therefore, it is 0.5 M/s, but since A is disappearing, it is 1.0 M/s.
Q. In a reaction at equilibrium, what effect does adding an inert gas at constant volume have?
A.
Shifts the equilibrium to the right
B.
Shifts the equilibrium to the left
C.
No effect on the 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.
Q. In a reaction at equilibrium, what effect does increasing the pressure have if the number of moles of gas on the reactant side is greater than on the product side?
A.
Shifts to the right
B.
Shifts to the left
C.
No effect
D.
Reaction stops
Solution
Increasing the pressure will shift the equilibrium to the right, favoring the side with fewer moles of gas.
Q. In a reaction at equilibrium, what effect does increasing the pressure have if the number of moles of gas on the reactant side is greater than that on the product side?
A.
Shifts to the right
B.
Shifts to the left
C.
No effect
D.
Reaction rate decreases
Solution
Increasing the pressure will shift the equilibrium to the right, favoring the side with fewer moles of gas, according to Le Chatelier's Principle.
Q. In a reaction at equilibrium, what happens if the concentration of reactants is increased?
A.
The equilibrium shifts to the right
B.
The equilibrium shifts to the left
C.
The equilibrium remains unchanged
D.
The reaction stops
Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right, favoring product formation.
Correct Answer:
A
— The equilibrium shifts to the right