Relevant Titles:
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CBSE Class 11 Chemistry MCQs – Atomic Mass and Chemical Formula Practice Test
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Class 11 Chemistry Chapter 1 MCQs – NCERT-Based Quiz on Atomic Mass and Formula
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Atomic Mass and Chemical Formula MCQs for CBSE Class 11 – Free Online Test
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📚 Introduction Paragraph
Understanding Atomic Mass and Chemical Formula is a crucial part of Chapter 1 – Some Basic Concepts of Chemistry in CBSE Class 11 Physical Chemistry. These concepts lay the groundwork for accurate chemical calculations, molecular composition, and stoichiometric understanding. This online MCQ practice test has been carefully curated following the latest NCERT Class 11 Chemistry syllabus, making it ideal for CBSE board exam preparation and foundational learning for competitive exams like JEE Main and NEET.
This quiz focuses on the calculation of atomic mass, molecular mass, formula units, isotopic abundance, and empirical versus molecular formulas. Each question helps students test their conceptual clarity and apply formulas to solve chemistry numericals accurately.
Attempting these Atomic Mass and Chemical Formula Class 11 MCQs not only boosts problem-solving confidence but also ensures precision and conceptual depth — essential for mastering Physical Chemistry at the Class 11 level.
🧩 Sample MCQs (with Answers & Explanations):
Q1. The relative atomic mass of chlorine is 35.45 because:
A. It’s an average of isotopic masses weighted by abundance
B. All chlorine atoms weigh 35.45 u
C. Its atomic number is 17
D. It has equal numbers of isotopes
✅ Answer: A
💡 Explanation: Chlorine exists mainly as ³⁵Cl and ³⁷Cl. The relative atomic mass (35.45) is the weighted average of these isotopes.
Q2. The molecular mass of CO₂ (C=12, O=16) is:
A. 28 u B. 32 u C. 44 u D. 16 u
✅ Answer: C
💡 Explanation: Molecular mass = 12 + 2×16 = 44 u.
Q3. The empirical formula of a compound with 40% carbon, 6.7% hydrogen, and 53.3% oxygen is:
A. CH₂O B. C₂H₄O₂ C. C₃H₆O₃ D. CHO
✅ Answer: A
💡 Explanation: The simplest whole-number ratio of C:H:O is 1:2:1 → empirical formula = CH₂O.
Q4. The molar mass of Na₂SO₄ (Na=23, S=32, O=16) is:
A. 120 g/mol B. 142 g/mol C. 100 g/mol D. 132 g/mol
✅ Answer: B
💡 Explanation: (23×2) + 32 + (16×4) = 142 g/mol.
Q5. The molecular formula of a compound is found to be C₄H₈. Its empirical formula is:
A. C₂H₄ B. CH₂ C. C₄H₈ D. C₂H₂
✅ Answer: B
💡 Explanation: The simplest ratio of C:H = 4:8 = 1:2, so the empirical formula is CH₂.