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Class XI · Chemistry

Some Basic Concepts in Chemistry: NEET MCQ practice

407 practice questions on Some Basic Concepts in Chemistry, each with an explanation. Practise them chapter by chapter in the GyaanLoop app.

407

Practice questions

200

Easy

199

Medium

8

Hard

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What Some Basic Concepts in Chemistry covers

Topics in the NEET (UG) 2026–27 syllabus for this chapter.

  • Matter and its nature, Dalton's atomic theory
  • Laws of chemical combination
  • Atomic and molecular masses, mole concept, molar mass
  • Percentage composition, empirical and molecular formulae
  • Chemical equations and stoichiometry

Sample questions on Some Basic Concepts in Chemistry

Try each one, then open the answer and explanation.

Question 1 · Practice question

C₂H 4 + xO 2 -> 2CO 2 + yH 2 O, what is the value of x + y?

  1. A.2
  2. B.3
  3. C.5
  4. D.8
Show answer

Answer: C. 5

Balancing C2H4 combustion gives C2H4 + 3O2 → 2CO2 + 2H2O, so x=3 and y=2, making x+y=5. The tempting choice (b) 3 might come from wrongly assuming x=y or adding wrong coefficients, but careful balancing leads to option C.

Question 2 · Practice question

0.4g of a polybasic acid H n A (all the hydrogens are acidic) requires 0.5g of NaOH for complete neutralization. The number of replaceable hydrogen atoms in the acid and the molecular weight of 'A' would be : (Molecular weight of the acid is 96 gms.)

  1. A.1, 95
  2. B.2, 94
  3. C.3, 93
  4. D.4,92
Show answer

Answer: C. 3, 93

The neutralization stoichiometry gives n × (mass acid / molar mass acid) = mass NaOH / molar mass NaOH. Solving yields n = 3, and since molar mass of HₙA is 96 g/mol, M(A) = 96 - 3 = 93. Don't mistakenly use n = 2 or 4; those fail to satisfy both the mole ratio and the given molar mass.

Question 3 · Practice question

1.0 mol of Fe reacts completely with 0.65 mol of O₂ to give a mixture of only Fe0 and Fe₂O₃. The mole ratio of ferrous oxide to ferric oxide is

  1. A.2 : 2
  2. B.4:3
  3. C.1:2
  4. D.2: 7
Show answer

Answer: B. 4:3

Assign variables for moles of FeO and Fe2O3, balance iron and oxygen atoms using the total Fe (1 mol) and total O atoms from O2, solve two equations to get mole numbers, then take the ratio. The correct 4:3 ratio matches option (b). Distraction (c) 1:2 would occur if you mistakenly assumed FeO and FeO3 or reversed coefficients.

Question 4 · Practice question

25 mL of a solution containing HCf and H₂ S0 4 required 10 mL of a 1 N NaOH solution for neutralization. 20 mL of the same acid mixture on being treated with an excess of AgNO₃ gives 0.1425 g of AgCf. The normality of the HC and the normality of the H₂ S0 4 are respectively

  1. A.0.40 N and 0.05 N
  2. B.0.05 N and 0.35 N
  3. C.0.50 N and 0.25 N
  4. D.0.40 N and 0.5 N
Show answer

Answer: B. 0.05 N and 0.35 N

The neutralisation condition gives N₁ + N₂ = 0.4, and the AgCl precipitation gives N₁ ≈ 0.05 from the given mass. Solving, N₂ = 0.35 N. Option (a) fails because 0.40 N and 0.05 N add to 0.45, not matching the neutralisation requirement. Option (b) fits both equations correctly.

Question 5 · Practice question

In the reaction: 2 C₂H 6 + 7 O₂ → 4 CO 2 + 6 H₂O how many moles of CO₂ are formed when 1 mole of O₂ is consumed?

  1. A.5 moles
  2. B.7/4 moles
  3. C.7 moles
  4. D.4/7 moles
Show answer

Answer: D. 4/7 moles

From the balanced equation, 7 moles of O₂ produce 4 moles of CO₂, so 1 mole of O₂ produces (4/7) moles of CO₂. Option (b) 7/4 moles incorrectly swaps the ratio, and others are distractors unrelated to stoichiometric coefficients.

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