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NEET Chemistry Some Basic Concepts of Chemistry Questions with Answers

Practise mole concept, stoichiometry, atomic mass, molar mass, concentration terms, limiting reagent and empirical-formula questions with clear answer explanations.

Practice Questions Explore Free NEET Tests
Overview Important Topics Formula Revision Questions with Answers Preparation Strategy FAQs
Chapter Overview

Some Basic Concepts of Chemistry for NEET

Some Basic Concepts of Chemistry is a core NEET Chemistry chapter because it introduces the mole concept and calculation methods used throughout Physical Chemistry. Questions often involve molar mass, Avogadro constant, stoichiometry, limiting reagent, percentage composition and concentration.

The main skill is converting the information given in a question into moles. Once the number of moles is known, you can use the balanced chemical equation, molar mass or concentration relation to reach the answer.

Study tip: Balance the chemical equation before using mole ratios. A correct calculation based on an unbalanced equation will still give the wrong answer.
High-yield Areas

Important Topics for NEET Basic Concepts of Chemistry

Revise these topics before attempting Some Basic Concepts of Chemistry MCQs or a chapter-wise NEET Chemistry practice test.

Mole Concept

Convert between mass, moles, number of particles and gas volume using molar mass and Avogadro constant.

Molar Mass

Calculate formula mass and molar mass correctly, including compounds with brackets and hydrated salts.

Stoichiometry

Use coefficients in a balanced equation to calculate reactant required, product formed or gas evolved.

Limiting Reagent

Compare available moles with the stoichiometric ratio and identify which reactant stops the reaction first.

Concentration Terms

Revise molarity, molality, mole fraction, mass percentage and parts per million.

Empirical Formula

Use percentage composition to obtain the simplest whole-number ratio of atoms.

Quick Revision

Some Basic Concepts of Chemistry Formula Revision

Use this formula list before practising numerical NEET Chemistry questions from this chapter.

Number of Moles\(n = \frac{\text{given mass}}{\text{molar mass}}\)
Number of Particles\(N = nN_A\), where \(N_A\) is Avogadro constant
Molarity\(M = \frac{\text{moles of solute}}{\text{volume of solution in litres}}\)
Molality\(m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}}\)
Mole Fraction\(X_A = \frac{n_A}{n_A+n_B+\cdots}\)
Mass Percentage\(\frac{\text{mass of component}}{\text{mass of solution}} \times 100\)
Percentage Yield\(\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\)
At STP ReferenceUse the gas-molar-volume condition specified in the question; do not assume a value if conditions differ.
NEET Chemistry Practice

Some Basic Concepts of Chemistry Questions with Answers

Attempt these original practice MCQs first. Open each explanation only after choosing an option.

10Practice MCQs
CoreMole concept and stoichiometry
ReviewStep-by-step explanations
Begin Question 1
Question Method

How to Solve Mole Concept Questions

  1. Write all given information with units and identify what has to be found.
  2. Convert mass, volume or particle count into moles wherever needed.
  3. Balance the chemical equation before applying coefficient ratios.
  4. For two reactants, calculate the product possible from each one to identify the limiting reagent.
  5. Check whether the final answer should be in mass, moles, molecules, concentration or percentage.
Practice MCQs

NEET Chemistry Some Basic Concepts of Chemistry Questions

These are original practice questions for revision. They are not presented as official NEET previous-year questions.

Question 1 · Mole Concept

The number of moles in 18 g of water \(H_2O\) is:

A. 0.5 mol
B. 1 mol
C. 2 mol
D. 18 mol
Show answer and explanation

Answer: B. Molar mass of water is \(2(1)+16=18\) g mol⁻¹. Therefore moles = \(18/18 = 1\) mol.

Question 2 · Avogadro Constant

One mole of any substance contains approximately:

A. \(6.022 \times 10^{20}\) particles
B. \(6.022 \times 10^{22}\) particles
C. \(6.022 \times 10^{23}\) particles
D. \(6.022 \times 10^{24}\) particles
Show answer and explanation

Answer: C. One mole contains Avogadro constant, approximately \(6.022 \times 10^{23}\) entities.

Question 3 · Molarity

What is the molarity of a solution prepared by dissolving 0.5 mol NaOH in enough water to make 250 mL solution?

A. 0.5 M
B. 1 M
C. 2 M
D. 4 M
Show answer and explanation

Answer: C. Volume = 250 mL = 0.250 L. Molarity = \(0.5/0.250 = 2\) M.

Question 4 · Stoichiometry

For \(2H_2 + O_2 \rightarrow 2H_2O\), how many moles of water are formed from 4 moles of \(H_2\) when oxygen is present in excess?

A. 1 mol
B. 2 mol
C. 4 mol
D. 8 mol
Show answer and explanation

Answer: C. The equation shows a 2:2 mole ratio between \(H_2\) and \(H_2O\). Therefore 4 moles of hydrogen form 4 moles of water.

Question 5 · Limiting Reagent

For \(N_2 + 3H_2 \rightarrow 2NH_3\), if 1 mol \(N_2\) reacts with 2 mol \(H_2\), the limiting reagent is:

A. \(N_2\)
B. \(H_2\)
C. \(NH_3\)
D. Neither reactant
Show answer and explanation

Answer: B. One mole of \(N_2\) requires 3 moles of \(H_2\), but only 2 moles are available. Hydrogen is limiting.

Question 6 · Empirical Formula

A compound contains 40% carbon, 6.67% hydrogen and 53.33% oxygen by mass. Its empirical formula is:

A. CHO
B. \(CH_2O\)
C. \(C_2H_4O_2\)
D. \(CHO_2\)
Show answer and explanation

Answer: B. Assume 100 g: moles C = \(40/12\), H = \(6.67/1\), O = \(53.33/16\). Dividing by the smallest gives approximately 1:2:1, hence \(CH_2O\).

Question 7 · Mole Fraction

A solution contains 2 mol ethanol and 8 mol water. The mole fraction of ethanol is:

A. 0.02
B. 0.20
C. 0.25
D. 0.80
Show answer and explanation

Answer: B. Mole fraction of ethanol = \(2/(2+8)=0.20\).

Question 8 · Formula Mass

The molar mass of \(CaCO_3\) is closest to:

A. 56 g mol⁻¹
B. 84 g mol⁻¹
C. 100 g mol⁻¹
D. 120 g mol⁻¹
Show answer and explanation

Answer: C. \(Ca=40\), \(C=12\), \(O_3=48\). Total = \(40+12+48=100\) g mol⁻¹.

Question 9 · Percentage Composition

The percentage by mass of oxygen in water \(H_2O\) is closest to:

A. 11.1%
B. 50.0%
C. 88.9%
D. 94.1%
Show answer and explanation

Answer: C. Oxygen contributes 16 g in 18 g water. Percentage = \((16/18)\times100\approx88.9\%\).

Question 10 · Molality

One mole of glucose is dissolved in 1 kg of water. The molality of the solution is:

A. 0.1 m
B. 0.5 m
C. 1 m
D. 2 m
Show answer and explanation

Answer: C. Molality is moles of solute per kilogram of solvent. Therefore \(1/1 = 1\) m.

Preparation Strategy

How to Prepare Some Basic Concepts of Chemistry for NEET

  1. Memorise common atomic masses that are used frequently in NEET-level calculations.
  2. Practise mass-to-mole and mole-to-particle conversions daily until they become quick.
  3. Balance every chemical equation before applying any mole ratio.
  4. For limiting-reagent questions, calculate possible product from both reactants before deciding.
  5. Keep concentration formulas separate and note their units: litres for molarity and kilograms of solvent for molality.

Common mistakes to avoid

  • Using volume of solvent instead of volume of solution in molarity questions.
  • Forgetting to convert millilitres into litres.
  • Applying a mole ratio before balancing the equation.
  • Using total solution mass instead of solvent mass in molality.
  • Ignoring the limiting reagent when both reactants are given.
FAQs

NEET Some Basic Concepts of Chemistry FAQs

Is the mole concept important for NEET Chemistry?

Yes. Mole concept and stoichiometry are used directly in this chapter and support many later Physical Chemistry calculations.

What are the most important topics in Some Basic Concepts of Chemistry?

Focus on mole concept, molar mass, stoichiometry, limiting reagent, concentration terms, percentage composition and empirical formula.

Are these official NEET previous-year questions?

No. The questions on this page are original practice questions for revision. Use official sources separately when checking exact previous-year papers and answer keys.

How should I solve limiting reagent questions?

Use the balanced equation, compare the required mole ratio with available moles, and identify which reactant produces the smaller amount of product.

Can I use this page as a NEET Chemistry chapter-wise test?

You can use these questions as a short practice set. For longer attempts, explore the available NEET mock tests and chapter-wise resources on PrepMocker.