All Free Chemistry MCQs with Answers
Every Chemistry question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,720 questions · page 574 of 686
- A. 1.008 mg
- B. 0.55 mg
- C. 1.09 mg
- D. 0.275 mg
Explanation: The mass of one mole of electrons is approximately 5.48579909070 × 10-4 grams.
Correct answer: 1.09 mg- A. 1.6 x 10^21
- B. 9.0 x 10^22
- C. 3.6 x 10^23
- D. 6.02 x 10^23
Explanation: To determine the total number of atoms in 0.125 moles of S8 molecules, we use the formula:Number of Atoms = Moles × Avogadro's Number ×…
Correct answer: 6.02 x 10^2311463. One mole of CO2 contains:
- A. 6.02 x 10^23 atoms of C
- B. 6.02 x 10^23 atoms of O
- C. 8.1 x 10^23 atoms of CO2
- D. 5.0 g atoms of CO2
Explanation: The correct option is A. 1 mole of any substance conatins Avagadro (NA = 6.02 x 1023) number of atoms.
Correct answer: 6.02 x 10^23 atoms of C11464. Choose the wrong statement:
- A. 1 mole means 6.023 x 10^23 particles.
- B. Molar mass is mass of 1 molecule.
- C. Molar mass is the mass of 1 mole of substance.
- D. Molar mass is molecular mass expressed in grams.
Explanation: Option B is incorrect. Molar mass is the mass of 1 mole of a substance and not the mass of molecule itself.
Correct answer: Molar mass is mass of 1 molecule.- A. 2.5 g
- B. 3 g
- C. 4 g
- D. 1 g
Explanation: We first have to find the moles of CO2. Since the volume of CO2 is given at STP, we can use the molar volume of a gas at STP, which is…
Correct answer: 4 g11466. 1 atomic mass unit=_kg
- A. 1.66 x 10^-27 kg
- B. 2.45 x 10^-31 kg
- C. 2.77 x 10^34 kg
- D. 9.34 x 10^-25 kg
Explanation: Fact, learn it (it is 1/12th the mass of Carbon-12).
Correct answer: 1.66 x 10^-27 kg- A. CO2
- B. HO
- C. H2
- D. H2O
Explanation: The empirical formula for water is H2O, which indicates that each molecule of water consists of 2 hydrogen atoms bonded to 1 oxygen atom.
Correct answer: H2O- A. 10NA
- B. 5.5NA
- C. 5
- D. 5NA
Explanation: Each Na+ has 10 electrons so in half mole of Na+ there will be 6.02x10^23 /2 ions.If we take 6.02x10^23 as NA 1 Na+ => 10 electrons NA/2…
Correct answer: 5NA- A. A limiting reagent is consumed at the end of the reaction
- B. Actual yield is always greater than theoretical yield
- C. Stoichiometric calculations can only be done if no side reaction happens
- D. The empirical formula and molecular formula of some compounds are the same
Explanation: Actual yield is less than theoretical yield due to the following reasons i) side reactions may produce by-productsii) some reactions are…
Correct answer: Actual yield is always greater than theoretical yield- A. Atomic meter unit.
- B. Atomic mass unified.
- C. Atomic mass unit.
- D. Atomic mass unity.
Explanation: The correct answer is 'Atomic mass unit'. The abbreviation 'amu' is commonly used in chemistry to denote a unit of mass that is precisely…
Correct answer: Atomic mass unit.- A. 342
- B. 343
- C. 341
- D. 340
Explanation: Molecular Mass of sucrose= (No. of Carbon x Atomic mass of carbon) + (No. of Hydrogen x Atomic mass of hydrogen) + (No.
Correct answer: 34211472. 1 atomic mass unit = _ kg
- A. 1.66×10-²⁷ kg
- B. 2.45×10-³¹ kg
- C. 2.77 x 10^34 kg
- D. 9.34×10-²⁵ kg
Explanation: The atomic mass unit (AMU or amu) of an element is a measure of its atomic mass.
Correct answer: 1.66×10-²⁷ kg- A. Electronic configuration is the same because atomic number is same.
- B. Isotopes have same atomic number.
- C. Isotopes of an element have different mass number.
- D. Isotopes of an element have different atomic number.
Explanation: The variation of atomic mass in isotopes can influence its physical properties like Density, Melting and boiling point and…
Correct answer: Isotopes of an element have different mass number.- A. 24.5g H2SO4
- B. 20g NaOH
- C. 46.5g NaOH
- D. 60g NaOH
Explanation: Mr of NaOH= 23 + 16 + 1 = 40g/molMr of H2SO4= (2x1) + 32 + (4x16) = 98g/mol2NaOH + H2SO4 => Na2SO4 +2H2O2x40g. 98g. xg.
Correct answer: 46.5g NaOH- A. 6.2 x 10^22
- B. 6.22 x 10^22
- C. 6.02 x 10^23
- D. 6.02 x 10^22
Explanation: Avogadro's law states that in one mole of any substance, a total number of 6.023×1023 molecules are present.
Correct answer: 6.02 x 10^2311476. When 8 grams (4 moles) of H2 react with 2 moles of O2 , how many moles of water will be formed?
- A. 5
- B. 4
- C. 6
- D. 3
Explanation: The balanced chemical equation for the reaction between hydrogen gas and oxygen gas to form water is:2H2 + O2 → 2H2OFrom the equation, we…
Correct answer: 4- A. Operational losses
- B. Reaction reversibility
- C. Side reaction
- D. All of these options are correct
Explanation: Usually, the actual yield is lower than the theoretical yield because few reactions truly proceed to completion (i.e., aren't 100%…
Correct answer: All of these options are correct- A. Reactant
- B. Products
- C. Both Options A and B are correct
- D. None of these options are correct
Explanation: The limiting reactant is the one that gets consumed first in a chemical reaction.
Correct answer: Products11479. A correct formula must:
- A. Always conform to the valency rules
- B. Always have a subscript of 1 for the first element
- C. Always have a subscript of 2 for the second element
- D. Always be written in alphabetical order of the elements
Explanation: This is the correct answer. A correct chemical formula must always conform to the valency rules.
Correct answer: Always conform to the valency rules- A. 25 NA
- B. 1.1 NA
- C. 2.5 NA
- D. 0.5 NA
Explanation: The Protium (hydrogen isotope) does not have any neutrons. We assume a deuterium isotope that has one neutron.
Correct answer: 2.5 NA