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 14 of 45
- A. 28.01 g
- B. 40.02 g
- C. 44.01 g
- D. 56.02 g
Explanation: The problem states the formula of substance X is AB₂. The molar mass of X is the sum of the masses of its components: (1 × 12.01) + (2 ×…
Correct answer: 44.01 g- A. 5 moles of C
- B. 8 moles of C
- C. 4 moles of C
- D. 13 moles of C
Explanation: First, identify the limiting reactant. Since 8 moles of B would only require 4 moles of A, B is the limiting reactant.
Correct answer: 4 moles of C- A. 12 g
- B. 4.4 g
- C. 44 g
- D. 440 g
Explanation: According to the balanced equation, 1 mole of lactose produces 12 moles of CO₂.
Correct answer: 44 g- A. The percent efficiency of the reaction
- B. The theoretical yield of the reaction
- C. The actual yield of the reaction
- D. The theoretical yield of the reactants
Explanation: The theoretical yield is the maximum possible quantity of a product that can be formed, calculated from the stoichiometry of the reaction.
Correct answer: The theoretical yield of the reaction- A. C₂H₄O₂
- B. CH₂O₂
- C. C₂H₂O₂
- D. CH₂O
Explanation: Convert the mass of each element to moles: Moles C = 24/12 = 2; Moles H = 4/1 = 4; Moles O = 32/16 = 2. The mole ratio C:H:O is 2:4:2.
Correct answer: CH₂O- A. M₂O
- B. M₂O₃
- C. MO
- D. M₃O₄
Explanation: Assuming a 100g sample, we have 40g O and 60g M. Converting to moles gives: 40g/16g/mol = 2.5 mol O, and 60g/24g/mol = 2.5 mol M.
Correct answer: MO- A. 1.9 x 10⁹
- B. 1.9 x 10¹⁰
- C. 1 x 10¹⁴
- D. 2 x 10¹¹
Explanation: To find the time, divide the total amount (Avogadro's number, ~6.02 × 10²³) by the rate of spending.
Correct answer: 1 x 10¹⁴268. How many water molecules will be lost on completely dehydrating 0.684 g of sucrose (C₁₂H₂₂O₁₁)?
- A. 1.32 x 10²²
- B. 6.02 x 10²⁰
- C. 6.62 x 10²¹
- D. 1.20 x 10²²
Explanation: First, find the moles of sucrose: 0.684 g / 342 g/mol = 0.002 mol. The dehydration reaction C₁₂H₂₂O₁₁ → 12C + 11H₂O shows 11 moles of…
Correct answer: 1.32 x 10²²- A. 0.5 NA
- B. NA
- C. 0.05 NA
- D. 1.6 NA
Explanation: First, find the moles of methane: 0.16 g / 16 g/mol = 0.01 mol. Each molecule of methane contains 5 atoms (1 C + 4 H).
Correct answer: 0.05 NA- A. 2
- B. 6
- C. 10
- D. 14
Explanation: The 3d subshell has 5 orbitals (d subshell: l = 2, m_l = -2, -1, 0, +1, +2), each holding 2 electrons. Thus, maximum electrons = 5 × 2 = 10.
Correct answer: 10- A. 80.09 g/mol
- B. 100.09 g/mol
- C. 120.09 g/mol
- D. 140.09 g/mol
Explanation: Molar mass = 40.08 (Ca) + 12.01 (C) + 3 × 16.00 (O) = 40.08 + 12.01 + 48.00 = 100.09 g/mol.
Correct answer: 100.09 g/mol- A. 50.0%
- B. 68.2%
- C. 90.9%
- D. 100.0%
Explanation: Moles of CH₄ = 10.0/16.05 ≈ 0.623 mol. Theoretical CO₂ = 0.623 mol × 44.01 = 27.42 g. Percent yield = (20.0/27.42) × 100 ≈ 68.2%.
Correct answer: 68.2%- A. CH₄
- B. C₂H₅
- C. CH₃
- D. CH₂
Explanation: Moles: C = 80/12 = 6.67, H = 20/1 = 20 → divide by smaller (6.67): CH₃.
Correct answer: CH₃- A. 2
- B. 4
- C. 8
- D. 6
Explanation: According to the balanced chemical equation: 2H₂ + O₂ → 2H₂O. This indicates that 2 moles of hydrogen gas react completely with 1 mole of…
Correct answer: 4- A. 22 g
- B. 28 g
- C. 44 g
- D. 11 g
Explanation: One mole of CaCO₃ (100 g) produces one mole of CO₂ (44 g). Therefore, 100 g CaCO₃ yields 44 g CO₂.
Correct answer: 44 g- A. N₂
- B. H₂
- C. Both in equal proportion
- D. None
Explanation: Moles N₂ = 28/28 = 1 mol; Moles H₂ = 9/2 = 4.5 mol. According ot balanced chemical equation: N₂ + 3H₂ → 2NH₃.
Correct answer: H₂- A. Fe
- B. O₂
- C. Both react completely
- D. None
Explanation: Balanced equation: 4Fe + 3O₂ → 2Fe₂O₃. For 2 mol O₂, 2.67 mol Fe are required; 3 mol Fe are present, so Fe is slightly in excess.
Correct answer: O₂- A. Cup
- B. Saucepan
- C. Glass
- D. Small bowl
Explanation: The rate of water evaporation depends on various factors such as the surface area exposed to air, temperature, humidity, and airflow.
Correct answer: Saucepan- A. Physical, atomic
- B. Physical, chemical
- C. Chemical, physical
- D. Chemical, atomic
Explanation: Different kinds of atoms of the same element, which have the same number of protons but different numbers of neutrons (resulting in…
Correct answer: Physical, chemical- A. Gram unit
- B. Avogadro's number
- C. Atomic mass
- D. Atomic mass unit
Explanation: One atomic mass unit (1amu) is a mass unit equal to exactly one-twelfth (1/12th) the mass of one atom of carbon-12 isotope, which is the…
Correct answer: Atomic mass unit