Major Competitive Exams

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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

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 concentration in g/L? (2020)

A. 20 g/L
B. 10 g/L
C. 5 g/L
D. 15 g/L

Solution

Concentration = (10 g / 0.5 L) = 20 g/L.

Correct Answer: A — 20 g/L

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Q. If 10 grams of NaCl is dissolved in 500 mL of water, what is the concentration in grams per liter? (2022)

A. 10 g/L
B. 20 g/L
C. 5 g/L
D. 15 g/L

Solution

Concentration = mass/volume = 10 g / 0.5 L = 20 g/L.

Correct Answer: A — 10 g/L

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Q. If 10 grams of NaCl is dissolved in 500 mL of water, what is the mass/volume percent concentration?

A. 1%
B. 2%
C. 5%
D. 10%

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 mass/volume percent concentration? (2020) 2020

A. 2%
B. 5%
C. 10%
D. 20%

Solution

Mass/volume % = (mass of solute / volume of solution) * 100 = (10 g / 500 mL) * 100 = 2%.

Correct Answer: B — 5%

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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

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

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

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

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

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 10 liters of a solution contains 30% salt, how much salt is present in the solution?

A. 3 liters
B. 2 liters
C. 4 liters
D. 1 liter

Solution

30% of 10 liters = 0.3 * 10 = 3 liters of salt.

Correct Answer: A — 3 liters

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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

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 g of water at 0°C is mixed with 100 g of water at 100°C, what will be the final temperature of the mixture?

A. 50°C
B. 25°C
C. 75°C
D. 0°C

Solution

Using the principle of conservation of energy, the final temperature will be 50°C.

Correct Answer: A — 50°C

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Q. If 100 g of water at 0°C is mixed with 100 g of water at 100°C, what will be the final temperature?

A. 50°C
B. 25°C
C. 75°C
D. 0°C

Solution

The final temperature will be 50°C due to equal masses and specific heat capacities.

Correct Answer: A — 50°C

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Q. If 100 g of water at 80°C is mixed with 200 g of water at 20°C, what will be the final temperature?

A. 30°C
B. 40°C
C. 50°C
D. 60°C

Solution

Using the principle of conservation of energy, the final temperature can be calculated to be 40°C.

Correct Answer: B — 40°C

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Q. If 100 J of heat is added to a system and 40 J of work is done by the system, what is the change in internal energy?

A. 60 J
B. 40 J
C. 100 J
D. 140 J

Solution

According to the First Law of Thermodynamics, ΔU = Q - W. Here, ΔU = 100 J - 40 J = 60 J.

Correct Answer: A — 60 J

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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

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 100 people were surveyed and 70 like pizza, 50 like pasta, and 20 like both, how many like neither?

A. 30
B. 20
C. 50
D. 40

Solution

Using inclusion-exclusion, the number of people who like either is 70 + 50 - 20 = 100, so 100 - 100 = 0 like neither.

Correct Answer: A — 30

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Q. If 1000 J of heat is added to a gas and it expands doing 400 J of work, what is the change in internal energy? (2023)

A. 600 J
B. 400 J
C. 1000 J
D. 200 J

Solution

Using the first law of thermodynamics: ΔU = Q - W = 1000 J - 400 J = 600 J.

Correct Answer: A — 600 J

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Q. If 1000 J of heat is added to a system and 400 J of work is done by the system, what is the change in internal energy of the system? (2021)

A. 600 J
B. 400 J
C. 1000 J
D. 200 J

Solution

Using the first law of thermodynamics: ΔU = Q - W = 1000 J - 400 J = 600 J.

Correct Answer: A — 600 J

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Q. If 1000 J of heat is added to a system and it does 400 J of work, what is the change in internal energy? (2021)

A. 600 J
B. 400 J
C. 1000 J
D. 1400 J

Solution

Using the first law of thermodynamics, ΔU = Q - W = 1000 J - 400 J = 600 J.

Correct Answer: A — 600 J

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Q. If 10^(2x) = 100, what is the value of x?

A. 0
B. 0.5
C. 1
D. 2

Solution

100 = 10^2, so 2x = 2, hence x = 1.

Correct Answer: B — 0.5

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Q. If 10^(x) = 1000, what is the value of x? (2023)

A. 2
B. 3
C. 4
D. 1

Solution

Since 1000 can be expressed as 10^3, we have 10^x = 10^3, thus x = 3.

Correct Answer: B — 3

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Q. If 10^(x+1) = 1000, what is the value of x?

A. 1
B. 2
C. 3
D. 4

Solution

1000 can be expressed as 10^3, so x + 1 = 3, leading to x = 2.

Correct Answer: B — 2

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Q. If 10^(x+2) = 1000, what is the value of x? (2023)

A. 1
B. 2
C. 3
D. 0

Solution

Since 1000 can be expressed as 10^3, we have 10^(x+2) = 10^3, thus x + 2 = 3, leading to x = 1.

Correct Answer: A — 1

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Q. If 10^x = 0.01, what is the value of x?

A. -2
B. -1
C. 0
D. 1

Solution

Since 0.01 = 10^(-2), we have x = -2.

Correct Answer: A — -2

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Q. If 12 men can complete a project in 30 days, how many men are needed to complete the project in 15 days?

A. 18 men
B. 24 men
C. 30 men
D. 36 men

Solution

If 12 men take 30 days, then to complete in 15 days, we need 12 * (30/15) = 24 men.

Correct Answer: B — 24 men

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Q. If 12 workers can complete a job in 15 days, how many days will it take for 6 workers to complete the same job?

A. 30 days
B. 45 days
C. 60 days
D. 75 days

Solution

Work done = Workers × Days; Total work = 12 × 15 = 180 worker-days; 6 workers will take 180/6 = 30 days.

Correct Answer: B — 45 days

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Q. If 15 g of sugar is dissolved in 300 mL of water, what is the concentration in g/mL? (2020)

A. 0.05 g/mL
B. 0.1 g/mL
C. 0.15 g/mL
D. 0.2 g/mL

Solution

Concentration = mass / volume = 15 g / 300 mL = 0.05 g/mL.

Correct Answer: B — 0.1 g/mL

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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

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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Major Competitive Exams

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