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 12 of 45
- A. 68,000 times
- B. 17,000 times
- C. 34,000 times
- D. 1,700 times
Explanation: To find the relative mass, divide the molecular weight of hemoglobin (~68,000 amu) by the atomic mass of helium (~4 amu).
Correct answer: 17,000 times- A. NH₄ ⁺
- B. H₃O⁺
- C. NH₃ ⁺
- D. SO₄ ²⁻
Explanation: A molecular ion is a charged species formed when a neutral molecule loses or gains an electron without breaking apart.
Correct answer: NH₃ ⁺- A. Chlorine
- B. Hydrogen
- C. Fluorine
- D. Cadmium
Explanation: A monoisotopic element has only one stable, naturally occurring isotope.
Correct answer: Fluorine- A. 1.2044 x 10²³
- B. 6.022 x 10²³
- C. 1.2044 x 10²⁴
- D. 2 x 6.022 x 10²²
Explanation: Sulfuric acid (H₂SO₄) produces two H⁺ ions, so 0.1 mol of H₂SO₄ yields 0.2 mol of H⁺ ions.
Correct answer: 1.2044 x 10²³- A. 0.08 g
- B. 0.80 g
- C. 8.0 g
- D. 80 g
Explanation: First, find the moles of O₂: (1.5 × 10²²) / (6.022 × 10²³) ≈ 0.025 mol. Then, calculate the mass: 0.025 mol × 32 g/mol (for O₂) = 0.8 g.
Correct answer: 0.80 g- A. More than 100
- B. 3
- C. 2
- D. Equal to 100
Explanation: The nucleus of an atom contains two types of fundamental particles, known as nucleons: the positively charged protons and the neutral…
Correct answer: 2227. Isotopes are:
- A. Chemically similar
- B. Chemically dissimilar
- C. Physically similar
- D. Both 'A' and 'B'
Explanation: Isotopes have the same number of protons and electrons, which determines their chemical behavior.
Correct answer: Chemically similar- A. Same number of neutrons
- B. Same mass number
- C. Same physical properties
- D. All of these
Explanation: Isotopes have different numbers of neutrons and therefore different mass numbers.
Correct answer: All of these229. What is the number of moles present in 0.6 grams of silica (SiO₂)? (Atomic mass Si = 28, O = 16):
- A. 0.01 mole
- B. 0.1 mole
- C. 0.06 mole
- D. 0.6 mole
Explanation: The molar mass of SiO₂ is 28 + (2 × 16) = 60 g/mol. The number of moles is the given mass divided by the molar mass: 0.6 g / 60 g/mol =…
Correct answer: 0.01 mole- A. 2.24 dm³
- B. 22.4 dm³
- C. 112 dm³
- D. 1.12 dm³
Explanation: First, find the moles of CO₂: 4.4 g / 44 g/mol = 0.1 mol. At STP, 1 mole of gas occupies 22.4 dm³.
Correct answer: 2.24 dm³- A. 0.25
- B. 0.50
- C. 1.00
- D. 1.50
Explanation: First, find the moles of oxygen atoms: 16 g / 16 g/mol = 1 mole of O atoms.
Correct answer: 0.50- A. 64 g
- B. 100 g
- C. 32 g
- D. 71 g
Explanation: Oxygen gas is diatomic (O₂), so its molar mass is 2 × 16 = 32 g/mol. The mass of 2 moles is therefore 2 mol × 32 g/mol = 64 g.
Correct answer: 64 g- A. 25 g of iodine
- B. 25 g mole of water
- C. 25 g atom of oxygen
- D. 25 g of nitrogen gas
Explanation: Calculate the mass of each option: A) 25 g; B) 25 moles × 18 g/mol (water) = 450 g; C) 25 moles × 16 g/mol (oxygen atoms) = 400 g; D) 25…
Correct answer: 25 g mole of water- A. Chemical change
- B. Physical change
- C. Neither chemical nor physical change
- D. Physical absorption of CO₂ in Mg(ClO₄)₂
Explanation: This is a chemical change because a reaction occurs where carbon dioxide (an acidic oxide) reacts with potassium hydroxide (a base) to…
Correct answer: Chemical change- A. H₂O
- B. C₆H₆
- C. H₂O₂
- D. NaCl
Explanation: The term "molecular formula" applies to substances made of discrete molecules.
Correct answer: NaCl- A. CO₂ and NH₃
- B. H₂O and Mg(ClO₄)₂
- C. CO₂ and KOH
- D. CO₂ and H₂O
Explanation: When a compound containing only carbon and hydrogen (a hydrocarbon) is burned completely in oxygen, the carbon forms carbon dioxide (CO₂)…
Correct answer: CO₂ and H₂O- A. 4
- B. 8
- C. 16
- D. 32
Explanation: From the formula H₂O, 0.5 moles of water must contain 0.5 moles of oxygen atoms.
Correct answer: 8- A. It contains 80 moles of atoms
- B. It contains 40 moles of hydrogen atoms
- C. It contains 30 moles of electrons
- D. It contains 30 moles of oxygen atoms
Explanation: In 20 moles of water (H₂O), there are 20 × 2 = 40 moles of hydrogen atoms and 20 × 1 = 20 moles of oxygen atoms.
Correct answer: It contains 40 moles of hydrogen atoms- A. C₆H₁₂O₆
- B. C₂H₆O
- C. C₁₂H₂₂O₁₁
- D. C₂H₄O
Explanation: A compound's molecular and empirical formulas are the same if the subscripts in the molecular formula cannot be simplified by a common…
Correct answer: C₁₂H₂₂O₁₁- A. 1° alcohol oxidizes to form an aldehyde, which can be further oxidized to a carboxylic acid
- B. 2° alcohol oxidizes to form a ketone
- C. 3° alcohol is easily oxidized in the presence of K₂Cr₂O₇/H₂SO₄
- D. All are correct statements
Explanation: This statement is incorrect because tertiary (3°) alcohols are resistant to oxidation.
Correct answer: 3° alcohol is easily oxidized in the presence of K₂Cr₂O₇/H₂SO₄