Mole Concept Practice Questions NEET: 6 Worked Solutions

Should I start Mole Concept practice with chapter MCQs or full mocks?

Start with worked Mole Concept practice questions for NEET if you still make conversion, counting or reaction-ratio errors. Use authentic chapter-wise previous-year questions next to check exam-style application, then full-length mocks to test execution inside a mixed paper.

This article contains six original, free, single-correct questions with worked solutions. It is an editorial practice set, not an official NEET paper or a PYQ collection.

A full mock is not the most efficient starting point for repairing one chapter. Fix the recurring error with chapter questions before testing it among other topics.

What do chapter questions, PYQs and full mocks actually test?

Chapter questions help repair a specific skill, PYQs check its use in authentic exam questions, and mocks test mixed-paper execution. Choose the format that tests your current weakness.

Chapter focus
This article: Six questions targeting conversions, particle counting, ratios, limiting reactants, purity and formula multipliers.
Authentic chapter-wise PYQs: Past exam questions selected for this chapter.
NEET JEEnius AI mocks: A full mixed-subject paper, not a dedicated Mole Concept set.
Main learning purpose
This article: Find the step you misunderstand.
PYQs: Check application in verified past-paper wording.
Mocks: Assess subject switching, time use and completion.
Explanation or feedback
This article: Worked solutions and error categories below.
PYQs: Solution quality depends on the source.
Mocks: A scored per-subject breakdown, which is not a verified Mole Concept diagnostic.
Access certainty
This article: These questions and solutions require no product signup.
PYQs: Free access depends on the source.
Mocks: 30 free full-length mocks a month, each with 180 questions, 720 marks and 180 minutes: 45 Physics, 45 Chemistry and 90 Biology questions.
What it cannot establish
This article: Complete chapter mastery or a predicted score.
PYQs: Authenticity without reliable paper provenance and answer keys.
Mocks: The verified specification does not establish the number of Mole Concept questions in an individual paper.

Which format should I choose in Class 11, Class 12 or a drop year?

Choose according to your errors, not your school year. A dropper who confuses atoms and molecules needs the same repair as a Class 11 student. Someone who explains chapter questions correctly but loses marks in mixed papers needs a different task.

Class 11, confusing atoms with molecules: Choose worked chapter questions. Explain the conversion from mass to moles, then molecules, then constituent atoms before moving to PYQs.
Class 12, direct conversions correct but reactions confusing: Use the diagnostic below to expose stoichiometry gaps. Repair the balanced-equation step before attempting authentic chapter-wise PYQs.
Dropper, comfortable with chapter questions but losing marks in mixed tests: Prioritise full mocks. Review wrong and unattempted Chemistry questions to separate knowledge gaps from time pressure or poor question selection.
Dropper, recurring foundational errors: Return to chapter practice. Completing more mocks is not evidence that the underlying error has disappeared.
Studying on a phone or with limited data: Attempt these on-page questions on paper. No video or downloadable PDF is needed.

Move forward when you can explain the relevant steps without copying a solution. A correct option alone is not enough, and an arbitrary accuracy threshold should not decide your next format.

Can I try six free Mole Concept practice questions for NEET now?

Attempt all six questions before scrolling to the answer key. These are original editorial practice questions, not official NEET questions or PYQs. Each has four options and exactly one correct answer under the stated conditions.

Write your option and one line of reasoning for each. All quantities are exercise givens, not exam statistics; masses, molar masses and initial sample amounts are positive. Letters represent numerical values in the specified units: for symbolic options, choose the expression valid for all allowed values.

Question 1: Mass to moles

A pure sample has the following mass and molar mass. What amount of substance does it contain?

Mass = m g, molar mass = M g m o l^{- 1}

A: & \frac{M}{m} m o l B: & \frac{m}{M} m o l C: & m M m o l D: & (m + M) m o l

Question 2: Molecules versus atoms

A sample contains the following amount of an intact diatomic substance. Choose the ordered pair giving its number of molecules first and its total number of constituent atoms second.

Substance: X_{2}, amount = n m o l, N_{A} = Avogadro constant in m o l^{- 1}

A: & (n m o l) N_{A}, (n m o l) N_{A} B: & 2 (n m o l) N_{A}, (n m o l) N_{A} C: & (n m o l) N_{A}, 2 (n m o l) N_{A} D: & \frac{1}{2} (n m o l) N_{A}, (n m o l) N_{A}

Question 3: Equal masses

Two pure molecular substances, P and Q, have equal sample masses and the molar masses shown below. Neither dissociates nor associates. What is the ratio of the number of P molecules to Q molecules?

M_{P} = M g m o l^{- 1}, M_{Q} = 2 M g m o l^{- 1}

A: & 2 : 1 B: & 1 : 2 C: & 1 : 1 D: & 4 : 1

Question 4: Limiting reactant

The model reaction below proceeds to completion with no side reactions. Initially, there is no product. Which option correctly identifies the limiting reactant and the amount of product formed? $A + 2 B ⟶ A B_{2}$

n_{A} = 3 m o l, n_{B} = 4 m o l

A: & A; 3 m o l of A B_{2} B: & B; 4 m o l of A B_{2} C: & A; 2 m o l of A B_{2} D: & B; 2 m o l of A B_{2}

Question 5: Purity before conversion

An impure sample has the total mass, pure-substance mass fraction and pure-substance molar mass given below. The impurity does not react. How many moles of the pure substance are available?

Total mass = m g, pure-substance mass fraction = p, 0 < p < 1, molar mass = M g m o l^{- 1}

The mass fraction is a decimal fraction, not a percentage number. Apply it to the total sample mass.

A: & \frac{m}{M} m o l B: & \frac{p m}{M} m o l C: & \frac{m}{p M} m o l D: & \frac{p M}{m} m o l

Question 6: Empirical to molecular formula

A compound has the empirical formula and molar masses specified below. What integer multiplier must be applied to every empirical-formula subscript to obtain its molecular formula? $Empirical formula: C H_{2}$

Molar mass of empirical-formula units = E g m o l^{- 1}

Molecular molar mass = 3 E g m o l^{- 1}

A: & 1 B: & 2 C: & 3 D: & 6

What are the answers, and which step caused my mistake?

The answer key is 1-B, 2-C, 3-A, 4-D, 5-B and 6-C. Check your reasoning, not just your selected option. For each error, use the category below to identify the step to repair.

1. Option B: Divide mass by molar mass.

The governing relationship converts grams into moles. The gram units cancel.

n = \frac{mass}{molar mass} = \frac{m g}{M g m o l^{- 1}} = \frac{m}{M} m o l

Option A reverses the division. Dividing molar mass by mass produces inverse-mole units, not moles; attaching “mol” does not fix it.

Any wrong option: unit or conversion error. Write the units in the division before calculating.

2. Option C: Count molecules before atoms.

One mole contains Avogadro’s number of the specified entity. Here, that entity is a molecule; each molecule then contributes two atoms.

A conversion chain labelled amount in moles, number of X2 molecules and total number of X atoms, with the first arrow labelled multiply by Avogadro constant and the second arrow labelled multiply by 2 atoms per molecule.

N_{molecules} = (n m o l) N_{A}

N_{atoms} = 2 N_{molecules} = 2 (n m o l) N_{A}

The mole units cancel against those in Avogadro’s constant, leaving particle counts. Option A misses the two atoms within each molecule.

Any wrong option: entity-counting error. Label the requested entity before using Avogadro’s constant.

3. Option A: Lower molar mass means more molecules at equal mass.

Let each sample have the same mass shown below. Convert each mass into moles, then molecules. $Common mass = w g$

\frac{N_{P}}{N_{Q}} = \frac{(\frac{w}{M} m o l) N_{A}}{(\frac{w}{2 M} m o l) N_{A}} = 2

The ratio is dimensionless. Doubling molar mass halves the number of molecules in the same mass, so option B reverses the relationship.

Any wrong option: inverse-ratio error. Write both mass-to-mole conversions before comparing.

4. Option D: B runs out first.

Divide each available amount by its balanced-equation coefficient. The smaller result determines how much reaction can occur.

\frac{n_{A}}{1} = 3 m o l, \frac{n_{B}}{2} = 2 m o l

n_{A B_{2}} = 1 \times min (3, 2) m o l = 2 m o l

Option A treats the smaller starting mole amount as automatically limiting. Comparing masses directly is also unreliable: reaction coefficients specify mole ratios, not mass ratios.

Any wrong option: stoichiometric-ratio error. Divide available moles by coefficients.

5. Option B: Apply purity first.

Find the pure-substance mass first. Only that mass belongs in its mass-to-mole conversion.

m_{pure} = p \times m g

n_{pure} = \frac{p m g}{M g m o l^{- 1}} = \frac{p m}{M} m o l

Option A counts the impurity as pure substance. Option C increases the calculated amount as purity falls, contradicting the sample description.

Any wrong option: purity error. Find usable mass before converting it.

6. Option C: The multiplier is the molar-mass ratio.

The empirical formula gives the simplest atom ratio. It does not necessarily give the atoms in one molecule.

k = \frac{M_{molecular}}{M_{empirical unit}} = \frac{3 E g m o l^{- 1}}{E g m o l^{- 1}} = 3

$(C H_{2})_{3} = C_{3} H_{6}$ The units cancel, leaving a dimensionless integer. Option B confuses the hydrogen subscript with the multiplier needed for every subscript.

Any wrong option: formula-multiplier error. Calculate the ratio before changing the formula.

What should I practise next, and when does a full mock help?

Repair the observed error, solve a changed question, then move to authentic PYQs. Use full mocks to assess chapter knowledge inside a mixed paper once you can explain your chapter solutions. These six Mole Concept practice questions for NEET cannot establish complete chapter mastery or predict a NEET score.

Conversion or counting wrong: Rewrite the quantity chain with units. Change the sample mass or molecular atomicity and solve again without consulting the solution.
Limiting reactant wrong: Rebuild the balanced-equation mole ratio before trying a longer calculation.
Another category wrong: Repeat that step with changed values. For purity, change the mass fraction; for molecular formulas, change the integer molar-mass relationship.
Correct answer, guessed explanation: Treat the concept as unfinished. Explain why the most tempting distractor fails.
Steps now secure: Attempt authentic chapter-wise PYQs whose paper provenance and answer key can be checked.

During mock review, use the official marking rule: +4 for correct, -1 for wrong and 0 for unattempted. The current structure has 180 compulsory questions and no optional Section B. Compulsory means there is no optional question section, not that you should guess blindly.

For mixed-paper practice, NEET JEEnius AI offers 30 free full-length mocks a month with a scored per-subject breakdown. After a mock, revisit each wrong or unattempted Chemistry question and write down the first step you could not justify.

Next step: full-length mock tests on NEET JEEnius AI and sit a full 180-question, 720-mark, 180-minute paper, 45 Physics, 45 Chemistry and 90 Biology, and get a scored per-subject breakdown (30 free a month).

Related on NEET JEEnius AI: Ecological Pyramids NEET 2026: Marine Biomass vs Energy.

Frequently asked questions

Should I start Mole Concept practice with chapter MCQs or full mocks?

Start with worked chapter questions if you still make conversion, particle-counting or reaction-ratio errors. Move to authentic chapter-wise PYQs once you can explain the steps without copying a solution. Use full mocks to test execution within a mixed paper.

Are these Mole Concept questions official NEET PYQs?

No. These are six original editorial practice questions, each with four options and one correct answer under the stated conditions. The questions and worked solutions are free to access without product signup.

How do I find the limiting reactant in Mole Concept questions?

Divide each reactant's available moles by its coefficient in the balanced equation. The smaller result identifies the limiting reactant. For A + 2B → AB₂ with 3 mol of A and 4 mol of B, B is limiting and 2 mol of AB₂ forms.

What should I do after solving these six Mole Concept questions?

Identify the first step you could not justify, repair it and solve a question with changed values without consulting the solution. Once you can explain the relevant steps, attempt authentic chapter-wise PYQs with verifiable paper sources and answer keys. Six correct answers alone do not establish complete chapter mastery or predict a NEET score.

Mole Concept Practice Questions NEET: 6 Worked Solutions

Should I start Mole Concept practice with chapter MCQs or full mocks?

What do chapter questions, PYQs and full mocks actually test?

Which format should I choose in Class 11, Class 12 or a drop year?

Can I try six free Mole Concept practice questions for NEET now?

What are the answers, and which step caused my mistake?

What should I practise next, and when does a full mock help?

Frequently asked questions

Should I start Mole Concept practice with chapter MCQs or full mocks?

Are these Mole Concept questions official NEET PYQs?

How do I find the limiting reactant in Mole Concept questions?

What should I do after solving these six Mole Concept questions?

Practise this with NEET JEEnius AI