Physical Chemistry
Q. If 1 mole of a non-electrolyte solute is dissolved in 1 kg of water, what is the expected freezing point depression?
A.
-1.86 °C
B.
-3.72 °C
C.
-0.52 °C
D.
-2.00 °C
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Solution
The freezing point depression is calculated using the formula ΔTf = Kf * m, where Kf for water is 1.86 °C kg/mol.
Correct Answer: A — -1.86 °C
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Q. If 1 mole of a non-electrolyte solute is dissolved in 1 kg of water, what is the freezing point depression?
A.
0 °C
B.
1.86 °C
C.
3.72 °C
D.
5.58 °C
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Solution
The freezing point depression is calculated using the formula ΔTf = i * Kf * m. For a non-electrolyte, i = 1, Kf for water = 1.86 °C kg/mol, and m = 1 mol/kg gives ΔTf = 1.86 °C.
Correct Answer: B — 1.86 °C
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Q. If 1 mole of a non-volatile solute is dissolved in 1 kg of water, what is the expected change in boiling point? (Kb for water = 0.512 °C kg/mol)
A.
0.512 °C
B.
1.024 °C
C.
2.048 °C
D.
0.256 °C
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Solution
Boiling point elevation = i * Kb * m = 1 * 0.512 * 1 = 0.512 °C.
Correct Answer: B — 1.024 °C
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Q. If 1 mole of NaCl is dissolved in 1 kg of water, what is the expected van 't Hoff factor (i)?
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Solution
NaCl dissociates into 2 ions (Na+ and Cl-), so the van 't Hoff factor (i) is 2.
Correct Answer: B — 2
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Q. If 1 mole of solute is dissolved in 1 liter of solution, what is the concentration in terms of molarity?
A.
1 M
B.
2 M
C.
0.5 M
D.
0.25 M
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Solution
Molarity (M) = moles of solute / liters of solution = 1 mole / 1 L = 1 M.
Correct Answer: A — 1 M
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Q. If 10 g of CaCO3 decomposes completely, how many grams of CO2 are produced?
A.
22 g
B.
10 g
C.
44 g
D.
20 g
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Solution
10 g of CaCO3 = 0.1 moles. CaCO3 → CaO + CO2, so 0.1 moles of CO2 = 0.1 * 44 g = 4.4 g.
Correct Answer: C — 44 g
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Q. If 10 g of Na reacts with excess Cl2, what is the mass of NaCl produced?
A.
58.5 g
B.
10 g
C.
20 g
D.
30 g
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Solution
10 g of Na = 0.43 moles. Na + Cl2 → NaCl, so 0.43 moles of NaCl = 0.43 * 58.5 g = 25.2 g.
Correct Answer: A — 58.5 g
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Q. If 10 grams of calcium carbonate (CaCO3) decomposes, how many grams of calcium oxide (CaO) are produced?
A.
5 g
B.
10 g
C.
8 g
D.
7 g
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Solution
The balanced equation is CaCO3 → CaO + CO2. The molar mass of CaCO3 is 100 g/mol and CaO is 56 g/mol. Thus, 10 g of CaCO3 produces (10 g / 100 g/mol) x 56 g/mol = 5.6 g of CaO.
Correct Answer: C — 8 g
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Q. If 10 grams of NaCl are dissolved in water, how many moles of NaCl are present? (Molar mass of NaCl = 58.5 g/mol)
A.
0.17 moles
B.
0.5 moles
C.
1.0 moles
D.
1.5 moles
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Solution
Moles of NaCl = mass (g) / molar mass (g/mol) = 10 g / 58.5 g/mol = 0.171 moles.
Correct Answer: A — 0.17 moles
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Q. If 10 grams of NaCl is dissolved in 500 mL of water, what is the mass/volume percent concentration?
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Solution
Mass/volume percent = (mass of solute / volume of solution) x 100 = (10 g / 500 mL) x 100 = 2%.
Correct Answer: B — 2%
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Q. If 10 grams of NaCl is dissolved in 500 mL of water, what is the molality of the solution? (Molar mass of NaCl = 58.5 g/mol)
A.
0.34 m
B.
0.17 m
C.
0.85 m
D.
0.50 m
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Solution
Molality (m) = moles of solute / kg of solvent. Moles of NaCl = 10 g / 58.5 g/mol = 0.171 moles. Mass of water = 0.5 kg. Molality = 0.171 moles / 0.5 kg = 0.342 m.
Correct Answer: A — 0.34 m
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Q. If 10 grams of NaCl is dissolved in enough water to make 500 mL of solution, what is the molality of the solution? (Molar mass of NaCl = 58.5 g/mol)
A.
0.34 m
B.
0.17 m
C.
0.85 m
D.
0.50 m
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Solution
Moles of NaCl = 10 g / 58.5 g/mol = 0.171 moles. Mass of solvent (water) = 0.5 kg. Molality (m) = moles of solute / kg of solvent = 0.171 moles / 0.5 kg = 0.34 m.
Correct Answer: A — 0.34 m
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Q. If 10 grams of NaOH are dissolved in water, how many moles of NaOH are present? (Molar mass of NaOH = 40 g/mol)
A.
0.25 moles
B.
0.5 moles
C.
1 mole
D.
2.5 moles
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Solution
To find the number of moles, use the formula: moles = mass/molar mass. Thus, 10 g / 40 g/mol = 0.25 moles.
Correct Answer: B — 0.5 moles
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Q. If 10 grams of NaOH is dissolved in 500 mL of solution, what is the molality of the solution? (Molar mass of NaOH = 40 g/mol)
A.
0.5 m
B.
1 m
C.
2 m
D.
0.25 m
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Solution
Moles of NaOH = 10 g / 40 g/mol = 0.25 moles. Mass of solvent (water) = 0.5 kg. Molality (m) = moles of solute / kg of solvent = 0.25 moles / 0.5 kg = 0.5 m.
Correct Answer: B — 1 m
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Q. If 10 grams of NaOH is dissolved in enough water to make 500 mL of solution, what is the molarity of the solution? (Molar mass of NaOH = 40 g/mol)
A.
0.5 M
B.
1 M
C.
2 M
D.
0.25 M
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Solution
Moles of NaOH = 10 g / 40 g/mol = 0.25 moles. Molarity = 0.25 moles / 0.5 L = 0.5 M.
Correct Answer: B — 1 M
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Q. If 100 g of glucose (C6H12O6) is dissolved in 1 L of solution, what is the molarity of the solution? (Molar mass of glucose = 180 g/mol)
A.
0.56 M
B.
1.0 M
C.
0.33 M
D.
0.75 M
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Solution
Moles of glucose = 100 g / 180 g/mol = 0.556 moles. Molarity = moles of solute / liters of solution = 0.556 moles / 1 L = 0.56 M.
Correct Answer: A — 0.56 M
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Q. If 100 J of heat is added to a system at a constant temperature of 300 K, what is the change in entropy?
A.
0.33 J/K
B.
0.25 J/K
C.
0.5 J/K
D.
0.75 J/K
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Solution
The change in entropy ΔS = Q/T = 100 J / 300 K = 0.33 J/K.
Correct Answer: A — 0.33 J/K
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Q. If 15 grams of HCl is dissolved in 500 mL of solution, what is the molarity of the solution? (Molar mass of HCl = 36.5 g/mol)
A.
0.82 M
B.
1.0 M
C.
0.5 M
D.
1.5 M
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Solution
Moles of HCl = 15 g / 36.5 g/mol = 0.41096 moles. Molarity = 0.41096 moles / 0.5 L = 0.82192 M.
Correct Answer: A — 0.82 M
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Q. If 15 grams of sugar is dissolved in 250 mL of water, what is the molarity of the solution? (Molar mass of sugar = 180 g/mol)
A.
0.33 M
B.
0.5 M
C.
0.25 M
D.
0.75 M
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Solution
Moles of sugar = 15 g / 180 g/mol = 0.0833 moles. Molarity = 0.0833 moles / 0.25 L = 0.333 M.
Correct Answer: A — 0.33 M
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Q. If 2 moles of a gas occupy 44.8 L at STP, what is the molar volume of the gas?
A.
22.4 L
B.
44.8 L
C.
11.2 L
D.
33.6 L
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Solution
At STP, 1 mole of gas occupies 22.4 L. Therefore, the molar volume of the gas is 22.4 L.
Correct Answer: A — 22.4 L
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Q. If 2 moles of glucose are dissolved in 1 liter of water, what is the molarity of the solution?
A.
1 M
B.
2 M
C.
0.5 M
D.
3 M
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Solution
Molarity = moles of solute / liters of solution = 2 moles / 1 L = 2 M.
Correct Answer: B — 2 M
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Q. If 2 moles of KCl are dissolved in 1 liter of solution, what is the molarity of the solution?
A.
1 M
B.
2 M
C.
0.5 M
D.
3 M
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Solution
Molarity (M) = moles of solute / liters of solution = 2 moles / 1 L = 2 M.
Correct Answer: B — 2 M
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Q. If 2 moles of NaCl are dissolved in 1 kg of water, what is the van 't Hoff factor (i)?
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Solution
NaCl dissociates into 2 ions (Na⁺ and Cl⁻), so the van 't Hoff factor (i) is 2.
Correct Answer: C — 3
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Q. If 20 grams of glucose (C6H12O6) is dissolved in 200 mL of solution, what is the mass percent concentration? (Molar mass of glucose = 180 g/mol)
A.
10%
B.
5%
C.
20%
D.
15%
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Solution
Mass percent = (mass of solute / total mass of solution) x 100 = (20 g / (20 g + 200 g)) x 100 = 10%.
Correct Answer: A — 10%
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Q. If 3 moles of a gas occupy 60 liters at STP, what is the molar volume of the gas?
A.
20 L
B.
30 L
C.
40 L
D.
60 L
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Solution
Molar volume = total volume / number of moles = 60 L / 3 moles = 20 L/mole.
Correct Answer: B — 30 L
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Q. If 3 moles of a gas occupy 60 liters, what is the volume occupied by 1 mole of the gas at the same conditions?
A.
20 L
B.
30 L
C.
15 L
D.
10 L
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Solution
Volume per mole = total volume / number of moles = 60 L / 3 moles = 20 L/mole.
Correct Answer: A — 20 L
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Q. If 4 moles of aluminum react with 3 moles of oxygen, how many moles of aluminum oxide are formed?
A.
2 moles
B.
3 moles
C.
4 moles
D.
6 moles
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Solution
The balanced equation is 4Al + 3O2 → 2Al2O3, which shows that 4 moles of Al produce 2 moles of Al2O3.
Correct Answer: A — 2 moles
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Q. If 4 moles of solute are dissolved in 2 kg of solvent, what is the molality of the solution?
A.
2 m
B.
4 m
C.
1 m
D.
0.5 m
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Solution
Molality (m) = moles of solute / kg of solvent = 4 moles / 2 kg = 2 m.
Correct Answer: A — 2 m
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Q. If 5 moles of KCl are dissolved in 1 kg of water, what is the molality of the solution?
A.
5 m
B.
2.5 m
C.
10 m
D.
1 m
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Solution
Molality (m) = moles of solute / kg of solvent = 5 moles / 1 kg = 5 m.
Correct Answer: A — 5 m
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Q. If 5 moles of KCl are dissolved in 3 kg of water, what is the molality of the solution?
A.
1.67 m
B.
2.5 m
C.
1.25 m
D.
0.5 m
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Solution
Molality (m) = moles of solute / kg of solvent = 5 moles / 3 kg = 1.67 m.
Correct Answer: A — 1.67 m
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