Free Fundamental Concepts of Chemistry MCQs with Answers
894 Fundamental Concepts of Chemistry MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Mole calculations connect mass, number of particles and Avogadro's number, while balanced equations provide the mole ratios used in stoichiometry. Questions cover limiting and excess reactants, theoretical yield and percentage yield, including identifying which reactant is consumed first and comparing the actual product with the maximum possible product.
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Read the Fundamental Concepts of Chemistry notesFree MDCAT chapter notes with key terms894 questions · page 13 of 45
- A. C₄H₆
- B. C₂H₆O
- C. C₂H₄O₂
- D. C₂H₄O
Explanation: The products correspond to 2 moles of C (from 88g CO₂) and 4 moles of H (from 36g H₂O). The mass of C+H is 28g.
Correct answer: C₂H₄O- A. C₉H₁₈O₉
- B. CH₂O
- C. C₆H₁₂O₆
- D. C₂H₄O₂
Explanation: The mass of the empirical formula (CH₂O) is 30 g/mol. The ratio of the molecular mass to the empirical mass is 180/30 = 6.
Correct answer: C₆H₁₂O₆- A. Empirical formula
- B. Molecular formula
- C. Ionic formula
- D. Covalent formula
Explanation: The molecular formula gives the exact number of atoms of each element in a single molecule of a substance.
Correct answer: Molecular formula- A. Ionic formula
- B. Structural formula
- C. Empirical formula
- D. Molecular formula
Explanation: The empirical formula is the most reduced representation of a compound's composition.
Correct answer: Empirical formula- A. H₂
- B. HO
- C. OH
- D. H₂O
Explanation: The molecular formula for water is H₂O. Since the 2:1 ratio of atoms cannot be simplified further into smaller whole numbers, the…
Correct answer: H₂O- A. Mg₂O₃
- B. MgO₂
- C. Mg₂O
- D. MgO
Explanation: Converting mass percentages to moles gives 2.5 mol Mg (60g/24g/mol) and 2.5 mol O (40g/16g/mol).
Correct answer: MgO- A. CCl₄
- B. CHCl₃
- C. CH₂Cl₂
- D. CH₂O
Explanation: The molecular formula for chloroform is CHCl₃. Since the 1:1:3 ratio of atoms cannot be simplified, the empirical formula is the same as…
Correct answer: CHCl₃- A. Number of ions
- B. Empirical formula of organic compounds
- C. Structural formula
- D. Isotopes of an element
Explanation: Combustion analysis is a method used to find the elemental composition of an organic compound.
Correct answer: Empirical formula of organic compounds- A. 12 times
- B. 1/12th
- C. 1/6th
- D. 6 times
Explanation: By international definition, one atomic mass unit (amu) is exactly equal to 1/12th of the mass of a single, neutral atom of the carbon-12…
Correct answer: 1/12th- A. Mass number - Atomic number
- B. Atomic number
- C. Number of electrons
- D. Mass number
Explanation: The mass number (A) is the total number of protons and neutrons. The atomic number (Z) is the number of protons.
Correct answer: Mass number - Atomic number- A. 11
- B. 23
- C. 12
- D. 22
Explanation: The atomic number of an element is defined as the number of protons in the nucleus of its atoms.
Correct answer: 11- A. 1.66×10⁻²⁷
- B. 2.45×10⁻³¹
- C. 2.77×10³⁴
- D. 9.34×10⁻²⁵
Explanation: The accepted conversion factor between the atomic mass unit (amu) and kilograms is 1 amu ≈ 1.66 × 10⁻²⁷ kg.
Correct answer: 1.66×10⁻²⁷- A. Isobars
- B. Isotopes
- C. Isotones
- D. Isomers
Explanation: Isotopes are atoms that have the same number of protons (making them the same element) but different numbers of neutrons, which results in…
Correct answer: Isotopes- A. Isotopes
- B. A half proton
- C. A half neutron
- D. A half electron
Explanation: The fractional atomic mass of chlorine is because it's a mixture of isotopes, primarily chlorine-35 and chlorine-37.
Correct answer: Isotopes- A. 1.0020
- B. 1.0180
- C. 1.0070
- D. 1.0080
Explanation: The atomic mass of hydrogen is the weighted average of its natural isotopes (¹H and ²H).
Correct answer: 1.0080- A. 340 grams of sucrose
- B. 344 grams of sucrose
- C. 342 grams of sucrose
- D. 346 grams of sucrose
Explanation: The molar mass of sucrose (C₁₂H₂₂O₁₁) is calculated by summing the atomic masses of all its atoms: (12×12.01) + (22×1.008) + (11×16.00) ≈…
Correct answer: 342 grams of sucrose- A. 21 times
- B. 22 times
- C. 23 times
- D. 24 times
Explanation: Using their approximate atomic masses, Sodium (Na) is ~23 amu and Hydrogen (H) is ~1 amu.
Correct answer: 23 times- A. Avogadro's number
- B. Molar mass
- C. Molar volume
- D. Mole
Explanation: Molar mass is the mass of one mole of a substance. It is numerically equal to the atomic, molecular, or formula mass expressed in atomic…
Correct answer: Molar mass- A. MnO₂
- B. MnO₃
- C. Mn₂O₃
- D. Mn₂O₇
Explanation: To find the maximum percentage, observe the mass ratio of oxygen to manganese (Mn ≈ 55, O ≈ 16).
Correct answer: Mn₂O₇- A. 2.5 g
- B. 3 g
- C. 4 g
- D. 6 g
Explanation: The 11.2 L of CO₂ produced at STP corresponds to 0.5 moles. According to the reaction C + O₂ → CO₂, this means 0.5 moles of carbon…
Correct answer: 4 g