Physical Chemistry
Q. In a binary solution of A and B, if component A has a higher vapor pressure than component B, what can be inferred about the solution?
A.
It will show positive deviation from Raoult's Law.
B.
It will show negative deviation from Raoult's Law.
C.
It will have a lower boiling point than pure A.
D.
It will have a higher boiling point than pure B.
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Solution
If component A has a higher vapor pressure than component B, the solution will show positive deviation from Raoult's Law.
Correct Answer: A — It will show positive deviation from Raoult's Law.
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Q. In a binary solution of A and B, if the mole fraction of A is 0.6, what is the mole fraction of B?
A.
0.4
B.
0.6
C.
1.0
D.
0.2
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Solution
The mole fraction of B can be calculated as 1 - mole fraction of A = 1 - 0.6 = 0.4.
Correct Answer: A — 0.4
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Q. In a binary solution of A and B, if the vapor pressure of A is 80 mmHg and that of B is 40 mmHg, what is the total vapor pressure of the solution if the mole fraction of A is 0.75?
A.
60 mmHg
B.
70 mmHg
C.
80 mmHg
D.
90 mmHg
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Solution
Total vapor pressure = P_A + P_B = (0.75 * 80) + (0.25 * 40) = 60 + 10 = 70 mmHg.
Correct Answer: D — 90 mmHg
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Q. In a binary solution of A and B, if the vapor pressure of pure A is 150 mmHg and pure B is 50 mmHg, what is the total vapor pressure when the mole fraction of A is 0.4?
A.
90 mmHg
B.
120 mmHg
C.
150 mmHg
D.
100 mmHg
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Solution
Total vapor pressure = (X_A * P_A^0) + (X_B * P_B^0) = (0.4 * 150) + (0.6 * 50) = 60 + 30 = 90 mmHg.
Correct Answer: B — 120 mmHg
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Q. In a binary solution of A and B, if the vapor pressure of pure A is 80 mmHg and that of pure B is 40 mmHg, what is the vapor pressure of the solution if the mole fraction of A is 0.6?
A.
64 mmHg
B.
72 mmHg
C.
80 mmHg
D.
56 mmHg
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Solution
Using Raoult's Law, the vapor pressure of the solution = (0.6 * 80 mmHg) + (0.4 * 40 mmHg) = 64 mmHg.
Correct Answer: B — 72 mmHg
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Q. In a binary solution of A and B, if the vapor pressure of pure A is 80 mmHg and pure B is 40 mmHg, what is the vapor pressure of the solution if the mole fraction of A is 0.6?
A.
64 mmHg
B.
72 mmHg
C.
80 mmHg
D.
56 mmHg
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Solution
Using Raoult's Law, the vapor pressure of the solution = (0.6 * 80 mmHg) + (0.4 * 40 mmHg) = 64 mmHg.
Correct Answer: B — 72 mmHg
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Q. In a binary solution of A and B, if the vapor pressure of pure A is 80 mmHg and pure B is 40 mmHg, what is the vapor pressure of component A if the mole fraction of A is 0.6?
A.
48 mmHg
B.
64 mmHg
C.
80 mmHg
D.
32 mmHg
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Solution
Using Raoult's Law, the vapor pressure of A in the solution is 0.6 * 80 mmHg = 48 mmHg.
Correct Answer: B — 64 mmHg
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Q. In a binary solution of A and B, if the vapor pressure of pure A is 80 mmHg and that of pure B is 40 mmHg, what is the total vapor pressure when the mole fraction of A is 0.6?
A.
64 mmHg
B.
72 mmHg
C.
80 mmHg
D.
88 mmHg
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Solution
Using Raoult's Law, the total vapor pressure = (0.6 * 80 mmHg) + (0.4 * 40 mmHg) = 48 mmHg + 16 mmHg = 64 mmHg.
Correct Answer: B — 72 mmHg
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Q. In a binary solution of A and B, if the vapor pressure of pure A is 80 mmHg and pure B is 40 mmHg, what is the total vapor pressure when the mole fraction of A is 0.5?
A.
60 mmHg
B.
70 mmHg
C.
80 mmHg
D.
50 mmHg
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Solution
Total vapor pressure = P_A + P_B = (0.5 * 80) + (0.5 * 40) = 40 + 20 = 60 mmHg.
Correct Answer: B — 70 mmHg
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Q. In a chemical reaction, if the enthalpy change is positive, the reaction is classified as:
A.
Exothermic
B.
Endothermic
C.
Isothermal
D.
Adiabatic
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Solution
A positive enthalpy change indicates that the reaction absorbs heat, classifying it as endothermic.
Correct Answer: B — Endothermic
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Q. In a chemical reaction, if the enthalpy of products is less than that of reactants, what can be concluded?
A.
The reaction is endothermic
B.
The reaction is exothermic
C.
The reaction is at equilibrium
D.
The reaction is spontaneous
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Solution
If the enthalpy of products is less, the reaction releases heat, indicating it is exothermic.
Correct Answer: B — The reaction is exothermic
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Q. In a closed system at equilibrium, if the pressure is increased, what will happen to the equilibrium position?
A.
Shift to the side with more moles of gas
B.
Shift to the side with fewer moles of gas
C.
No change
D.
Increase in temperature
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Solution
Increasing the pressure will shift the equilibrium position to the side with fewer moles of gas.
Correct Answer: B — Shift to the side with fewer moles of gas
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Q. In a closed system at equilibrium, if the volume is decreased, what will happen to the equilibrium position?
A.
Shift to the side with more moles of gas
B.
Shift to the side with fewer moles of gas
C.
No change
D.
Increase in pressure
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Solution
Decreasing the volume increases the pressure, and the equilibrium will shift to the side with fewer moles of gas to counteract the change.
Correct Answer: B — Shift to the side with fewer moles of gas
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Q. In a closed system, if the temperature increases, what happens to the entropy?
A.
It decreases
B.
It increases
C.
It remains constant
D.
It becomes zero
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Solution
In a closed system, an increase in temperature generally leads to an increase in entropy, as the molecular motion becomes more chaotic.
Correct Answer: B — It increases
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Q. In a closed system, if the volume of gas is halved at constant temperature, what happens to the pressure?
A.
Halved
B.
Doubled
C.
Remains the same
D.
Increases four times
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Solution
According to Boyle's law, if the volume is halved, the pressure is doubled.
Correct Answer: B — Doubled
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Q. In a concentration cell, the potential difference arises due to:
A.
Different temperatures
B.
Different concentrations
C.
Different pressures
D.
Different materials
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Solution
In a concentration cell, the potential difference arises due to different concentrations of the same species.
Correct Answer: B — Different concentrations
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Q. In a Daniell cell, which metal is oxidized?
A.
Copper
B.
Zinc
C.
Lead
D.
Silver
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Solution
In a Daniell cell, zinc is oxidized.
Correct Answer: B — Zinc
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Q. In a dynamic equilibrium, which of the following statements is true?
A.
The rates of the forward and reverse reactions are equal
B.
The concentrations of reactants and products are equal
C.
The reaction has stopped
D.
The system is at rest
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Solution
In a dynamic equilibrium, the rates of the forward and reverse reactions are equal, but the concentrations of reactants and products may not be equal.
Correct Answer: A — The rates of the forward and reverse reactions are equal
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Q. In a first-order reaction, if the concentration of the reactant is halved, what happens to the half-life?
A.
It doubles
B.
It remains the same
C.
It is halved
D.
It becomes zero
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Solution
In a first-order reaction, the half-life is independent of the concentration of the reactant, so it remains the same.
Correct Answer: B — It remains the same
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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 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?
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 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 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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