Mole Concept: Essential Study for Competitive Exams

Mole Concept

Q. How many atoms are in 2 moles of oxygen gas (O2)?

A. 6.022 x 10^23
B. 1.2044 x 10^24
C. 3.011 x 10^23
D. 12.044 x 10^23

Solution

Each O2 molecule has 2 oxygen atoms. Number of atoms = moles x Avogadro's number x 2 = 2 moles x 6.022 x 10^23 molecules/mole x 2 = 1.2044 x 10^24 atoms.

Correct Answer: B — 1.2044 x 10^24

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Q. How many grams are in 0.25 moles of glucose (C6H12O6)?

A. 30 g
B. 45 g
C. 75 g
D. 90 g

Solution

Molar mass of C6H12O6 = 6*12 + 12*1 + 6*16 = 180 g/mol. Mass = 0.25 moles x 180 g/mol = 45 g.

Correct Answer: D — 90 g

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Q. How many grams are in 0.25 moles of KCl?

A. 35 g
B. 70 g
C. 17.5 g
D. 140 g

Solution

Molar mass of KCl = 39 + 35.5 = 74.5 g/mol. Mass = moles x molar mass = 0.25 moles x 74.5 g/mol = 18.625 g.

Correct Answer: B — 70 g

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Q. How many grams are in 0.25 moles of sulfuric acid (H2SO4)?

A. 49 g
B. 98 g
C. 24.5 g
D. 12.25 g

Solution

Molar mass of H2SO4 = 98 g/mol. Mass = moles x molar mass = 0.25 moles x 98 g/mol = 24.5 g.

Correct Answer: A — 49 g

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Q. How many grams are in 3 moles of glucose (C6H12O6)?

A. 180 g
B. 360 g
C. 540 g
D. 90 g

Solution

Molar mass of glucose = 6*12 + 12*1 + 6*16 = 180 g/mol. Mass = moles x molar mass = 3 moles x 180 g/mol = 540 g.

Correct Answer: B — 360 g

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Q. How many molecules are present in 2 moles of water (H2O)?

A. 6.022 x 10^23
B. 1.2044 x 10^24
C. 3.011 x 10^23
D. 12.044 x 10^24

Solution

Number of molecules = moles x Avogadro's number = 2 moles x 6.022 x 10^23 molecules/mole = 1.2044 x 10^24 molecules.

Correct Answer: B — 1.2044 x 10^24

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Q. How many moles are in 1.5 kg of KCl?

A. 10
B. 20
C. 15
D. 5

Solution

Molar mass of KCl = 39 + 35.5 = 74.5 g/mol. Number of moles = mass/molar mass = 1500 g / 74.5 g/mol ≈ 20.1 moles.

Correct Answer: B — 20

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Q. How many moles are in 10 grams of NaOH?

A. 0.25
B. 0.5
C. 0.75
D. 1

Solution

Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol. Number of moles = mass/molar mass = 10 g / 40 g/mol = 0.25 moles.

Correct Answer: A — 0.25

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Q. How many moles are in 100 grams of CaCO3?

A. 1
B. 2
C. 0.5
D. 0.25

Solution

Molar mass of CaCO3 = 40 + 12 + 3*16 = 100 g/mol. Number of moles = mass/molar mass = 100 g / 100 g/mol = 1 mole.

Correct Answer: A — 1

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Q. How many moles are in 180 grams of water?

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

Solution

Molar mass of H2O = 2*1 + 16 = 18 g/mol. Number of moles = 180 g / 18 g/mol = 10 moles.

Correct Answer: A — 1

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Q. How many moles are in 200 grams of H2O?

A. 11.11
B. 10
C. 9
D. 8.89

Solution

Molar mass of H2O = 18 g/mol. Number of moles = mass / molar mass = 200 g / 18 g/mol = 11.11 moles.

Correct Answer: A — 11.11

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Q. How many moles are in 200 grams of H2SO4?

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

Solution

Molar mass of H2SO4 = 2 + 32 + 16*4 = 98 g/mol. Number of moles = 200 g / 98 g/mol = 2.04 moles.

Correct Answer: B — 2

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Q. How many moles are in 36 grams of water (H2O)?

A. 1
B. 2
C. 0.5
D. 3

Solution

Molar mass of H2O = 2*1 + 16 = 18 g/mol. Number of moles = mass/molar mass = 36 g / 18 g/mol = 2 moles.

Correct Answer: A — 1

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Q. How many moles are in 5.6 liters of a gas at STP?

A. 0.25
B. 0.5
C. 1
D. 2

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?

A. 0.25
B. 0.5
C. 1
D. 2

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?

A. 0.5
B. 1
C. 1.25
D. 2

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?

A. 1
B. 0.5
C. 2
D. 0.25

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?

A. 0.5
B. 1
C. 2
D. 4

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?

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

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?

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

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)?

A. 2
B. 1
C. 4
D. 0.5

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. 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
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 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 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

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

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. What is the mass of 0.5 moles of CaCO3?

A. 50 g
B. 25 g
C. 100 g
D. 75 g

Solution

Molar mass of CaCO3 = 40 + 12 + 16*3 = 100 g/mol. Mass = moles x molar mass = 0.5 moles x 100 g/mol = 50 g.

Correct Answer: B — 25 g

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Q. What is the mass of 0.5 moles of NaCl?

A. 29 g
B. 58 g
C. 14 g
D. 0.5 g

Solution

Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol. Mass = moles x molar mass = 0.5 moles x 58.5 g/mol = 29.25 g.

Correct Answer: A — 29 g

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Mole Concept MCQ & Objective Questions

The Mole Concept is a fundamental topic in chemistry that plays a crucial role in various examinations. Understanding this concept not only helps in grasping the basics of chemical calculations but also enhances problem-solving skills. Practicing MCQs and objective questions related to the Mole Concept is essential for students aiming to score better in their exams. By tackling these practice questions, you can identify important questions and strengthen your exam preparation.

What You Will Practise Here

Definition and significance of a mole in chemistry
Conversions between moles, mass, and number of particles
Avogadro's Law and its applications
Calculating molar mass and its importance
Stoichiometry and its relation to the Mole Concept
Limiting reactants and yield calculations
Real-life applications of the Mole Concept in various chemical reactions

Exam Relevance

The Mole Concept is a vital part of the syllabus for CBSE, State Boards, NEET, and JEE. Questions related to this topic often appear in various formats, including numerical problems, theoretical questions, and conceptual MCQs. Students can expect to encounter questions that require them to calculate moles, apply stoichiometric principles, and interpret chemical equations. Familiarity with common question patterns will greatly enhance your confidence during exams.

Common Mistakes Students Make

Confusing moles with mass and volume, leading to incorrect conversions
Overlooking the significance of Avogadro's number in calculations
Misunderstanding stoichiometric ratios in chemical reactions
Failing to identify limiting reactants in problems
Neglecting to practice unit conversions, which can lead to errors in answers

FAQs

Question: What is a mole in chemistry?
Answer: A mole is a unit that measures the amount of substance, defined as containing exactly 6.022 x 10²³ particles, such as atoms or molecules.

Question: How do I calculate the molar mass of a compound?
Answer: To calculate the molar mass, sum the atomic masses of all the atoms in the compound's formula, expressed in grams per mole.

Now is the time to sharpen your skills! Dive into our practice MCQs on the Mole Concept and test your understanding. By solving these important Mole Concept questions for exams, you will be well-prepared to tackle any challenge that comes your way. Start practicing today!

Mole Concept

Mole Concept MCQ & Objective Questions

What You Will Practise Here

Exam Relevance

Common Mistakes Students Make

FAQs

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