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Some Basic Concepts of Chemistry — NEET & JEE Chemistry MCQs

30 questions written by hand against the NCERT chapter. Every wrong option is explained, not just the right one.

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Sample questions from this chapter

Which observation identifies a sample as a mixture rather than a pure compound?
  1. Its components can occur in variable proportions and be separated by physical methods ✓
  2. Its constituent elements occur in a fixed mass ratio
  3. Every particle has the same chemical composition
  4. Its components lose their individual properties through chemical bonding
Answer: A. A mixture has variable composition and its components retain enough identity for physical separation. The closest trap is the fixed-ratio statement, which describes a compound, not a homogeneous mixture.
Why not B: A fixed elemental mass ratio is characteristic of a pure compound under the law of definite proportions.
Why not C: Identical chemical particles describe a pure substance rather than a mixture.
Why not D: Chemical bonding creates a compound; mixture components retain their identities and can often be separated physically.
A liquid has density 2.50 g cm^-3. What is this density in kg m^-3?
  1. 2.50 kg m^-3
  2. 250 kg m^-3
  3. 2.50 × 10^3 kg m^-3 ✓
  4. 2.50 × 10^4 kg m^-3
Answer: C. 1 g cm^-3 = (10^-3 kg)/(10^-6 m^3) = 10^3 kg m^-3. Therefore 2.50 g cm^-3 equals 2.50 × 10^3 kg m^-3.
Why not A: This changes the unit labels without applying either the gram-to-kilogram or cubic-centimetre-to-cubic-metre factor.
Why not B: This applies a factor of 100, as though the centimetre conversion were linear rather than cubic.
Why not D: This uses a net factor of 10^4, commonly produced by cubing 100 but mishandling the 10^-3 gram-to-kilogram conversion.
An iron oxide contains 69.9% Fe and 30.1% O by mass. What is its empirical formula? Use Fe = 55.85 and O = 16.00.
  1. Fe2O3 ✓
  2. FeO
  3. FeO3
  4. Fe3O2
Answer: A. In 100 g, Fe gives 69.9/55.85 = 1.252 mol and O gives 30.1/16.00 = 1.881 mol. Division by 1.252 gives 1:1.50; doubling both terms yields Fe2O3.
Why not B: FeO results from rounding the calculated O:Fe mole ratio of about 1.50 directly to 1 instead of clearing the half by multiplying both ratios by 2.
Why not C: FeO3 results from converting 1.50 to 3 for oxygen but failing to multiply the iron ratio by the same factor of 2.
Why not D: Fe3O2 reverses the correctly cleared Fe:O ratio of 2:3.

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Other NEET Chemistry chapters

Structure of AtomClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureThermodynamicsEquilibriumRedox Reactions

All 19 chapters →

Questions

How many NEET and JEE questions are there on Some Basic Concepts of Chemistry?

This chapter test has 30 questions — 10 easy, 14 medium and 6 hard — all written against the NCERT Class 11 chapter.

Is this NEET and JEE Chemistry chapter test free?

Yes. Every chapter test is free with no login, and you get your all-India rank on every one. Nothing on the site is on sale right now.

Do the questions explain the wrong options?

Yes — every distractor carries its own explanation naming the specific misconception that makes a student pick it. That is the part most question banks skip, and it is the part that changes your next attempt.