Q. A solution has a concentration of 0.1 M NaCl. How many grams of NaCl are present in 1 liter of this solution? (Molar mass of NaCl = 58.5 g/mol)
A.5.85 g
B.58.5 g
C.0.1 g
D.0.585 g
Solution
Mass = moles x molar mass = 0.1 moles x 58.5 g/mol = 5.85 g.
Correct Answer: B — 58.5 g
Q. A solution has a concentration of 0.2 M. How many moles of solute are present in 1.5 L of this solution?
A.0.3 moles
B.0.5 moles
C.0.2 moles
D.0.15 moles
Solution
Moles of solute = Molarity × Volume = 0.2 M × 1.5 L = 0.3 moles.
Correct Answer: B — 0.5 moles
Q. A solution is prepared by dissolving 50 g of glucose (C6H12O6) in 250 g of water. What is the mass percent of glucose in the solution? (Molar mass of glucose = 180 g/mol)
A.20%
B.15%
C.25%
D.10%
Solution
Mass percent = (mass of solute / (mass of solute + mass of solvent)) × 100 = (50 g / (50 g + 250 g)) × 100 = 20%.
Correct Answer: A — 20%
Q. A solution is prepared by dissolving 58.5 g of NaCl in 1 L of water. What is the molarity of the solution? (Molar mass of NaCl = 58.5 g/mol)
A.1 M
B.2 M
C.0.5 M
D.0.1 M
Solution
Moles of NaCl = 58.5 g / 58.5 g/mol = 1 mole. Molarity = moles of solute / liters of solution = 1 mole / 1 L = 1 M.
Correct Answer: A — 1 M
Q. A solution is prepared by dissolving 58.5 g of NaCl in enough water to make 1 L of solution. What is the molarity of the solution? (Molar mass of NaCl = 58.5 g/mol)
A.1 M
B.2 M
C.0.5 M
D.0.1 M
Solution
Moles of NaCl = 58.5 g / 58.5 g/mol = 1 mole. Molarity = 1 mole / 1 L = 1 M.
Correct Answer: A — 1 M
Q. According to Boyle's law, if the volume of a gas is doubled at constant temperature, what happens to the pressure?
A.It doubles
B.It halves
C.It remains constant
D.It quadruples
Solution
Boyle's law states that pressure is inversely proportional to volume at constant temperature, so if the volume is doubled, the pressure halves.
Correct Answer: B — It halves
Q. According to Boyle's law, if the volume of a gas is doubled, what happens to its pressure?
A.It doubles
B.It halves
C.It remains constant
D.It quadruples
Solution
Boyle's law states that pressure is inversely proportional to volume at constant temperature, so if volume is doubled, pressure is halved.
Correct Answer: B — It halves
Q. According to the ideal gas law, which of the following is the correct equation?
A.PV = nRT
B.PV = nR
C.P = nRT/V
D.V = nP/RT
Solution
The ideal gas law is represented by the equation PV = nRT.
Correct Answer: A — PV = nRT
Q. According to VSEPR theory, what is the shape of the molecule with the formula AX2E2?
A.Linear
B.Bent
C.Trigonal planar
D.Tetrahedral
Solution
AX2E2 indicates two bonding pairs and two lone pairs, resulting in a bent shape.
Correct Answer: B — Bent
Q. At what temperature does the Gibbs Free Energy change from negative to positive?
A.At absolute zero
B.At the melting point
C.At the boiling point
D.At the transition temperature
Solution
The Gibbs Free Energy changes from negative to positive at the transition temperature, where the system shifts from one phase to another.
Correct Answer: D — At the transition temperature
Q. For a first-order reaction, the half-life is independent of the initial concentration. What is the expression for half-life?
A.t1/2 = 0.693/k
B.t1/2 = k/0.693
C.t1/2 = 1/k
D.t1/2 = k/2
Solution
For a first-order reaction, the half-life is given by the expression t1/2 = 0.693/k.
Correct Answer: A — t1/2 = 0.693/k
Q. For a first-order reaction, the half-life is independent of which of the following?
A.Initial concentration
B.Rate constant
C.Temperature
D.All of the above
Solution
For a first-order reaction, the half-life is independent of the initial concentration.
Correct Answer: A — Initial concentration
Q. For 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
Solution
If doubling the concentration of A doubles the rate, the reaction is first order with respect to A.
Correct Answer: B — First order
Q. For a reaction at constant temperature and pressure, which of the following is true?
A.ΔG = ΔH + TΔS
B.ΔG = ΔH - TΔS
C.ΔG = TΔS - ΔH
D.ΔG = ΔS - ΔH
Solution
The correct relationship at constant temperature and pressure is ΔG = ΔH - TΔS.
Correct Answer: B — ΔG = ΔH - TΔS
Q. For a reaction at standard conditions, if ΔG° is positive, what does it imply?
A.The reaction is spontaneous in the forward direction.
B.The reaction is at equilibrium.
C.The reaction is non-spontaneous in the forward direction.
D.The reaction will proceed rapidly.
Solution
A positive ΔG° indicates that the reaction is non-spontaneous in the forward direction under standard conditions.
Correct Answer: C — The reaction is non-spontaneous in the forward direction.
Q. For a reaction with ΔH = 100 kJ/mol and ΔS = 200 J/mol·K, at what temperature will the reaction become spontaneous?
A.500 K
B.250 K
C.200 K
D.100 K
Solution
To find the temperature at which the reaction becomes spontaneous, set ΔG = 0: 0 = ΔH - TΔS, thus T = ΔH/ΔS = 100,000 J / 200 J/K = 500 K.
Correct Answer: A — 500 K
Q. For a reaction with ΔH = 50 kJ/mol and ΔS = 100 J/mol·K, at what temperature will the reaction become spontaneous?
A.500 K
B.250 K
C.1000 K
D.200 K
Solution
To find the temperature at which the reaction becomes spontaneous, set ΔG = 0: 0 = ΔH - TΔS, thus T = ΔH/ΔS = (50,000 J/mol) / (100 J/mol·K) = 500 K.
Correct Answer: A — 500 K
Q. For a reversible process, the change in entropy of the system is equal to the heat absorbed divided by the temperature. This is expressed as:
A.ΔS = Q/T
B.ΔS = T/Q
C.ΔS = Q + T
D.ΔS = Q - T
Solution
For a reversible process, the change in entropy (ΔS) is given by ΔS = Q/T, where Q is the heat absorbed and T is the temperature.
Correct Answer: A — ΔS = Q/T
Q. For a solution to obey Raoult's Law, the interactions between solute and solvent must be:
A.Stronger than those in the pure components.
B.Weaker than those in the pure components.
C.Similar to those in the pure components.
D.Non-existent.
Solution
For a solution to obey Raoult's Law, the interactions between solute and solvent must be similar to those in the pure components.
Correct Answer: C — Similar to those in the pure components.
Q. For a spontaneous process, the change in entropy of the universe must be:
A.Zero
B.Positive
C.Negative
D.Undefined
Solution
For a spontaneous process, the total entropy change of the universe (system + surroundings) must be positive.
Correct Answer: B — Positive
Q. For a spontaneous process, the change in Gibbs free energy (ΔG) is related to entropy (ΔS) how?
A.ΔG = ΔH - TΔS
B.ΔG = TΔS - ΔH
C.ΔG = ΔS - ΔH
D.ΔG = ΔH + TΔS
Solution
The relationship is given by ΔG = ΔH - TΔS, where ΔG must be negative for a spontaneous process.
Correct Answer: A — ΔG = ΔH - TΔS
Q. For a spontaneous process, the change in Gibbs free energy (ΔG) is related to entropy (ΔS) by which of the following equations?
A.ΔG = ΔH + TΔS
B.ΔG = ΔH - TΔS
C.ΔG = TΔS - ΔH
D.ΔG = ΔS - ΔH
Solution
The correct relationship is ΔG = ΔH - TΔS, where ΔG must be negative for a spontaneous process.
Correct Answer: B — ΔG = ΔH - TΔS
Q. For a spontaneous process, the change in Gibbs free energy (ΔG) is:
A.Positive
B.Negative
C.Zero
D.Undefined
Solution
For a process to be spontaneous, the change in Gibbs free energy (ΔG) must be negative.
Correct Answer: B — Negative
Q. For an electron in a 3p orbital, what are the possible values of m_l?
A.-1, 0, +1
B.0, +1, +2
C.-2, -1, 0
D.0, -1, -2
Solution
For a p orbital, l=1, so m_l can take values -1, 0, +1.
Correct Answer: A — -1, 0, +1
Q. For an electron in a 3p orbital, what are the possible values of the magnetic quantum number (m_l)?
A.-1, 0, +1
B.0, +1, +2
C.-2, -1, 0
D.1, 2, 3
Solution
For a p orbital (l=1), m_l can take values -1, 0, +1.
Correct Answer: A — -1, 0, +1
Q. For an ideal solution, if the mole fraction of the solvent is 0.75, what is the vapor pressure of the solution if the vapor pressure of the pure solvent is 100 mmHg?
A.75 mmHg
B.100 mmHg
C.25 mmHg
D.50 mmHg
Solution
According to Raoult's Law, the vapor pressure of the solution is 0.75 * 100 mmHg = 75 mmHg.
Correct Answer: A — 75 mmHg
Q. For the equilibrium 2A(g) ⇌ B(g) + C(g), how many moles of gas are on the reactant side?
A.1
B.2
C.3
D.4
Solution
There are 2 moles of gas on the reactant side (2A).
Correct Answer: B — 2
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
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
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
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
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
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.
