Q. In a galvanic cell, the anode is where:
A.
Reduction occurs
B.
Oxidation occurs
C.
Electrons are gained
D.
The salt bridge is located
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Solution
In a galvanic cell, oxidation occurs at the anode.
Correct Answer: B — Oxidation occurs
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Q. In a galvanic cell, which electrode undergoes reduction?
A.
Anode
B.
Cathode
C.
Salt bridge
D.
Electrolyte
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Solution
In a galvanic cell, reduction occurs at the cathode.
Correct Answer: B — Cathode
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Q. In a reaction A → B, if the concentration of A decreases from 0.5 M to 0.1 M in 20 minutes, what is the average rate of reaction?
A.
0.02 M/min
B.
0.04 M/min
C.
0.05 M/min
D.
0.06 M/min
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Solution
Average rate = (change in concentration) / (time) = (0.5 - 0.1) / 20 = 0.02 M/min.
Correct Answer: B — 0.04 M/min
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Q. In a reaction A → B, if the rate of formation of B is 0.1 mol/L·s, what is the rate of disappearance of A?
A.
0.1 mol/L·s
B.
0.05 mol/L·s
C.
0.2 mol/L·s
D.
0.1 L/mol·s
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Solution
For the reaction A → B, the rate of disappearance of A is equal to the rate of formation of B, hence it is 0.1 mol/L·s. However, if stoichiometry is considered as 1:1, the rate of disappearance of A is also 0.1 mol/L·s.
Correct Answer: C — 0.2 mol/L·s
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Q. In a reaction A → B, if the rate of formation of B is 0.5 mol/L·s, what is the rate of disappearance of A?
A.
0.5 mol/L·s
B.
1.0 mol/L·s
C.
0.25 mol/L·s
D.
0.75 mol/L·s
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Solution
For the reaction A → B, the rate of disappearance of A is equal to the rate of formation of B, thus it is 1.0 mol/L·s.
Correct Answer: B — 1.0 mol/L·s
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Q. In a reaction A → B, if the rate of reaction doubles when the concentration of A is doubled, what is the order of the reaction with respect to A?
A.
Zero order
B.
First order
C.
Second order
D.
Third order
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Solution
If the rate doubles when the concentration of A is doubled, the reaction is first order with respect to A.
Correct Answer: B — First order
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Q. In a reaction at equilibrium, if the concentration of a reactant is decreased, what will happen?
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, decreasing the concentration of a reactant will shift the equilibrium to the left to produce more reactants.
Correct Answer: B — Shift to the left
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Q. In a reaction at equilibrium, if the concentration of products increases, 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, if the concentration of products increases, the equilibrium will shift to the left.
Correct Answer: A — Shift to the left
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Q. In a reaction at equilibrium, if the concentration of products is decreased, what will happen?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on the temperature
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Solution
Decreasing the concentration of products will shift the equilibrium to the right to produce more products, according to Le Chatelier's principle.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the concentration of reactants is increased, what will happen to the equilibrium position?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on the reaction
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right to produce more products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the concentration of reactants is increased, what will happen to the equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Equilibrium constant increases
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium to the right to form more products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the temperature is decreased, what will happen to the equilibrium position if the reaction is exothermic?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on the concentration
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Solution
For an exothermic reaction, decreasing the temperature shifts the equilibrium to the right, favoring the formation of products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the temperature is increased and the reaction is exothermic, what will happen to the equilibrium position?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Equilibrium constant increases
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Solution
For an exothermic reaction, increasing the temperature shifts the equilibrium position to the left, favoring the reactants.
Correct Answer: B — Shift to the left
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Q. In a reaction at equilibrium, if the temperature is increased, what will happen to the equilibrium constant Kc for an endothermic reaction?
A.
Increase
B.
Decrease
C.
No change
D.
Depends on concentration
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Solution
For an endothermic reaction, increasing temperature shifts the equilibrium to the right, increasing Kc.
Correct Answer: A — Increase
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Q. In a reaction mechanism, the slowest step is known as the:
A.
Rate-determining step
B.
Intermediate step
C.
Fast step
D.
Catalytic step
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Solution
The slowest step in a reaction mechanism is called the rate-determining step, as it controls the overall reaction rate.
Correct Answer: A — Rate-determining step
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Q. In a reaction mechanism, the slowest step is known as what?
A.
Rate-determining step
B.
Intermediate step
C.
Fast step
D.
Catalytic step
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Solution
The slowest step in a reaction mechanism is known as the rate-determining step.
Correct Answer: A — Rate-determining step
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Q. In a reaction where 2 moles of hydrogen react with 1 mole of oxygen, how many moles of water are produced?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
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Solution
According to the balanced equation 2H2 + O2 → 2H2O, 2 moles of H2 produce 2 moles of H2O.
Correct Answer: B — 2 moles
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Q. In a reaction where ΔH is negative and ΔS is positive, what can be said about ΔG?
A.
ΔG is always negative.
B.
ΔG is always positive.
C.
ΔG is zero.
D.
ΔG depends on temperature.
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Solution
If ΔH is negative and ΔS is positive, ΔG will always be negative at all temperatures.
Correct Answer: A — ΔG is always negative.
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Q. In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?
A.
Positive
B.
Negative
C.
Zero
D.
Cannot be determined
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Solution
At high temperatures, ΔG will be positive because the positive ΔH and negative ΔS will dominate the equation ΔG = ΔH - TΔS.
Correct Answer: A — Positive
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Q. In a reaction, 3 moles of A react with 2 moles of B to produce 4 moles of C. What is the mole ratio of A to C?
A.
3:4
B.
2:3
C.
4:3
D.
1:1
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Solution
The mole ratio of A to C is 3:4 based on the coefficients in the balanced equation.
Correct Answer: A — 3:4
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Q. In a reaction, if the enthalpy change (ΔH) is -100 kJ and the entropy change (ΔS) is 200 J/K, what is the Gibbs free energy change (ΔG) at 298 K?
A.
-100 kJ
B.
-50 kJ
C.
0 kJ
D.
50 kJ
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Solution
ΔG = ΔH - TΔS = -100 kJ - (298 K * 0.2 kJ/K) = -100 kJ - 59.6 kJ = -159.6 kJ.
Correct Answer: A — -100 kJ
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Q. In a reaction, if the rate constant doubles when the temperature increases by 10°C, what is the activation energy (Ea) approximately?
A.
20 kJ/mol
B.
40 kJ/mol
C.
60 kJ/mol
D.
80 kJ/mol
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Solution
Using the Arrhenius equation, Ea can be estimated to be around 40 kJ/mol.
Correct Answer: B — 40 kJ/mol
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Q. In a redox reaction, which species is reduced?
A.
Oxidizing agent
B.
Reducing agent
C.
Product
D.
Reactant
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Solution
The oxidizing agent is the species that gains electrons and is reduced.
Correct Answer: A — Oxidizing agent
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Q. In a reversible process, the change in entropy of the universe is:
A.
Positive
B.
Negative
C.
Zero
D.
Undefined
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Solution
In a reversible process, the change in entropy of the universe is zero, as the system and surroundings are in equilibrium.
Correct Answer: C — Zero
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Q. In a reversible process, the change in Gibbs free energy (ΔG) is:
A.
Always positive
B.
Always negative
C.
Zero at equilibrium
D.
None of the above
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Solution
In a reversible process, the change in Gibbs free energy (ΔG) is zero at equilibrium.
Correct Answer: C — Zero at equilibrium
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Q. In a reversible process, the change in Gibbs free energy is equal to:
A.
Zero
B.
Enthalpy
C.
Entropy
D.
Temperature
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Solution
In a reversible process at equilibrium, the change in Gibbs free energy is zero.
Correct Answer: A — Zero
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Q. In a solution of 0.1 M NH4Cl, what is the pH if the Kb of NH3 is 1.8 x 10^-5?
A.
4.75
B.
5.75
C.
6.75
D.
7.75
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Solution
Using the formula for weak bases, pH = 14 - pKb = 14 - (14 - 4.75) = 5.75.
Correct Answer: B — 5.75
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Q. In a solution of 1 mol of solute in 9 mol of solvent, what is the mole fraction of the solute?
A.
0.1
B.
0.2
C.
0.5
D.
0.9
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Solution
Mole fraction of solute = moles of solute / (moles of solute + moles of solvent) = 1 / (1 + 9) = 0.1.
Correct Answer: A — 0.1
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Q. In a solution of 1 mole of solute B in 3 moles of solvent A, what is the mole fraction of solvent A?
A.
0.25
B.
0.75
C.
0.33
D.
0.67
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Solution
Mole fraction of A = moles of A / (moles of A + moles of B) = 3 / (3 + 1) = 0.75.
Correct Answer: B — 0.75
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Q. In a solution of a non-volatile solute, how does the addition of solute affect the boiling point of the solvent?
A.
It decreases the boiling point
B.
It has no effect on the boiling point
C.
It increases the boiling point
D.
It depends on the nature of the solute
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Solution
The addition of a non-volatile solute raises the boiling point of the solvent, a phenomenon known as boiling point elevation.
Correct Answer: C — It increases the boiling point
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