Physical Chemistry
Q. How many moles are in 5.6 liters of a gas at STP?
Solution
At STP, 1 mole of gas occupies 22.4 L. Number of moles = volume / molar volume = 5.6 L / 22.4 L/mole = 0.25 moles.
Correct Answer: C — 1
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Q. How many moles are in 5.6 liters of an ideal gas at STP?
Solution
At STP, 1 mole of gas occupies 22.4 L. Therefore, number of moles = 5.6 L / 22.4 L/mole = 0.25 moles.
Correct Answer: B — 0.5
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Q. How many moles are in 50 grams of CaCO3?
Solution
Molar mass of CaCO3 = 100 g/mol. Number of moles = mass / molar mass = 50 g / 100 g/mol = 0.5 moles.
Correct Answer: B — 1
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Q. How many moles are in 50 grams of H2O?
-
A.
2.78
-
B.
1.39
-
C.
0.56
-
D.
3.06
Solution
Molar mass of H2O = 2*1 + 16 = 18 g/mol. Number of moles = mass/molar mass = 50 g / 18 g/mol = 2.78 moles.
Correct Answer: B — 1.39
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Q. How many moles are in 50 grams of NaOH?
Solution
Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol. Number of moles = mass/molar mass = 50 g / 40 g/mol = 1.25 moles.
Correct Answer: B — 0.5
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Q. How many moles are in 50 grams of sodium (Na)?
-
A.
1.08
-
B.
2.5
-
C.
0.5
-
D.
0.25
Solution
Molar mass of Na = 23 g/mol. Number of moles = mass / molar mass = 50 g / 23 g/mol ≈ 2.17 moles.
Correct Answer: A — 1.08
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Q. How many moles are in 500 mL of a 2 M NaCl solution?
Solution
Moles = molarity x volume (in L) = 2 M x 0.5 L = 1 mole.
Correct Answer: B — 1
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Q. How many moles are in 88 grams of CH4?
Solution
Molar mass of CH4 = 12 + 4*1 = 16 g/mol. Number of moles = mass/molar mass = 88 g / 16 g/mol = 5.5 moles.
Correct Answer: B — 2
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Q. How many moles are in 88 grams of O2?
Solution
Molar mass of O2 = 16*2 = 32 g/mol. Number of moles = mass/molar mass = 88 g / 32 g/mol = 2.75 moles.
Correct Answer: B — 2
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Q. How many moles are in 88 grams of oxygen (O2)?
Solution
Molar mass of O2 = 32 g/mol. Number of moles = mass / molar mass = 88 g / 32 g/mol = 2.75 moles.
Correct Answer: A — 2
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Q. How many moles of CO2 are produced from the complete combustion of 1 mole of C3H8?
Solution
C3H8 + 5O2 → 3CO2 + 4H2O. 1 mole of C3H8 produces 3 moles of CO2.
Correct Answer: A — 3
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Q. How many moles of KCl are produced when 2 moles of K react with 2 moles of Cl2?
-
A.
1 mole
-
B.
2 moles
-
C.
3 moles
-
D.
4 moles
Solution
The balanced equation is 2K + Cl2 → 2KCl. Therefore, 2 moles of K will produce 2 moles of KCl.
Correct Answer: B — 2 moles
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Q. How many moles of oxygen are required to completely react with 4 moles of ethane (C2H6)?
-
A.
5 moles
-
B.
7 moles
-
C.
8 moles
-
D.
10 moles
Solution
The balanced equation is 2C2H6 + 7O2 → 4CO2 + 6H2O. Therefore, 4 moles of C2H6 require 14 moles of O2, which means 7 moles of O2 for 2 moles of C2H6.
Correct Answer: B — 7 moles
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Q. Identify the hybridization of the central atom in NH3.
-
A.
sp
-
B.
sp2
-
C.
sp3
-
D.
dsp3
Solution
The nitrogen atom in NH3 is sp3 hybridized, forming three bonds and one lone pair.
Correct Answer: C — sp3
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Q. Identify the hybridization of the nitrogen atom in NH3.
-
A.
sp
-
B.
sp2
-
C.
sp3
-
D.
dsp2
Solution
The nitrogen atom in NH3 is sp3 hybridized, forming three N-H bonds and one lone pair.
Correct Answer: C — sp3
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Q. If 0.1 M of a weak acid has a pH of 4.0, what is the Ka of the acid?
-
A.
1 x 10^-4
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B.
1 x 10^-5
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C.
1 x 10^-6
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D.
1 x 10^-7
Solution
Using the formula Ka = [H+]^2 / [HA], where [H+] = 10^(-4) M and [HA] = 0.1 M, we find Ka = (10^-4)^2 / 0.1 = 1 x 10^-5.
Correct Answer: B — 1 x 10^-5
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Q. If 0.5 mol of a non-volatile solute is dissolved in 1 kg of water, what is the vapor pressure lowering? (Vapor pressure of pure water = 23.76 mmHg)
-
A.
1.88 mmHg
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B.
2.88 mmHg
-
C.
3.88 mmHg
-
D.
4.88 mmHg
Solution
Vapor pressure lowering = (n_solute / n_solvent) * P°_solvent = (0.5 / 55.5) * 23.76 = 1.88 mmHg
Correct Answer: A — 1.88 mmHg
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Q. If 0.5 moles of a gas occupy 11.2 liters at STP, what is the molar volume of the gas?
-
A.
22.4 L
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B.
11.2 L
-
C.
5.6 L
-
D.
44.8 L
Solution
At STP, 1 mole of gas occupies 22.4 L. Therefore, the molar volume is 22.4 L.
Correct Answer: A — 22.4 L
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Q. If 0.5 moles of NaCl are dissolved in 1 liter of water, what is the concentration of NaCl?
-
A.
0.5 M
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B.
1 M
-
C.
2 M
-
D.
0.25 M
Solution
Concentration (M) = moles of solute / liters of solution = 0.5 moles / 1 L = 0.5 M.
Correct Answer: A — 0.5 M
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Q. If 0.5 moles of NaCl are dissolved in 1 liter of water, what is the concentration of NaCl in the solution?
-
A.
0.5 M
-
B.
1 M
-
C.
2 M
-
D.
0.25 M
Solution
Concentration (M) = moles of solute / liters of solution = 0.5 moles / 1 L = 0.5 M.
Correct Answer: A — 0.5 M
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Q. If 0.5 moles of NaCl are dissolved in 1 liter of water, what is the molarity of the solution?
-
A.
0.5 M
-
B.
1 M
-
C.
2 M
-
D.
0.25 M
Solution
Molarity (M) = moles of solute / liters of solution = 0.5 moles / 1 L = 0.5 M.
Correct Answer: A — 0.5 M
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Q. If 1 L of a 2 M solution is diluted to 3 L, what is the new molarity of the solution?
-
A.
0.67 M
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B.
1 M
-
C.
1.5 M
-
D.
2 M
Solution
Using the dilution formula M1V1 = M2V2, we have 2 M * 1 L = M2 * 3 L, thus M2 = 2/3 = 0.67 M.
Correct Answer: A — 0.67 M
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Q. If 1 L of a 3 M solution is diluted to 2 L, what is the new molarity?
-
A.
1.5 M
-
B.
3 M
-
C.
6 M
-
D.
0.5 M
Solution
Using the dilution formula M1V1 = M2V2, we have 3 M × 1 L = M2 × 2 L. Thus, M2 = 1.5 M.
Correct Answer: A — 1.5 M
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Q. If 1 liter of a 2 M solution is diluted to 3 liters, what is the new molarity?
-
A.
0.67 M
-
B.
1 M
-
C.
1.5 M
-
D.
2 M
Solution
Using the dilution formula M1V1 = M2V2, (2 M)(1 L) = M2(3 L) => M2 = 2/3 = 0.67 M.
Correct Answer: A — 0.67 M
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Q. If 1 mol of NaCl is dissolved in 1 kg of water, how many particles are present in solution?
Solution
NaCl dissociates into 2 ions (Na+ and Cl-), so 1 mol of NaCl produces 2 mol of particles in solution.
Correct Answer: B — 2
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Q. If 1 mol of NaCl is dissolved in 1 kg of water, what is the expected van 't Hoff factor (i)?
Solution
NaCl dissociates into 2 ions (Na+ and Cl-), so the van 't Hoff factor i = 2.
Correct Answer: B — 2
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Q. If 1 mol of NaCl is dissolved in water, how many particles are present in solution?
Solution
NaCl dissociates into 2 ions (Na+ and Cl-), so 1 mol of NaCl results in 2 mol of particles.
Correct Answer: B — 2
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Q. If 1 mole of a gas occupies 22.4 L at STP, how many liters will 0.5 moles occupy?
-
A.
11.2 L
-
B.
22.4 L
-
C.
44.8 L
-
D.
5.6 L
Solution
Volume = moles x volume per mole = 0.5 moles x 22.4 L/mole = 11.2 L.
Correct Answer: A — 11.2 L
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Q. If 1 mole of a gas occupies 22.4 L at STP, how much volume will 0.5 moles occupy?
-
A.
11.2 L
-
B.
22.4 L
-
C.
44.8 L
-
D.
5.6 L
Solution
Volume = moles x volume per mole = 0.5 moles x 22.4 L/mole = 11.2 L.
Correct Answer: A — 11.2 L
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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
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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