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 1 of 45
- A. 6.02 x 10^-23
- B. 6.02 x 10^23
- C. 6.02 x 10^24
- D. 3.01 x 10^23
Explanation: One mole of any substance contains 6.02 x 10^23 particles, whether those particles are atoms, molecules or ions.
Correct answer: 6.02 x 10^23- A. the amount containing as many particles as there are atoms in 12 g of carbon 12
- B. one gram of the substance
- C. the mass of one molecule of the substance
- D. the volume occupied by one gram of a gas
Explanation: The mole is a counting unit fixed by reference to 12 g of carbon 12, which is why the molar mass of any substance in grams contains…
Correct answer: the amount containing as many particles as there are atoms in 12 g of carbon 12- A. 0.5
- B. 1
- C. 2
- D. 18
Explanation: The molar mass of water is 2(1) + 16, that is 18 g per mole, so 36 divided by 18 gives 2 moles.
Correct answer: 2- A. 6.02 x 10^23
- B. 3.01 x 10^23
- C. 44
- D. 1.204 x 10^24
Explanation: Two moles contain 2 x 6.02 x 10^23, which is 1.204 x 10^24 molecules, and this is true for any substance since the mole counts particles…
Correct answer: 1.204 x 10^24- A. 22.4 dm3
- B. 24 dm3
- C. 1 dm3
- D. 22.4 cm3
Explanation: At 273 K and 1 atmosphere one mole of any gas occupies 22.4 dm3, which follows from the ideal gas equation and is independent of the…
Correct answer: 22.4 dm3- A. 40 g
- B. 20 g
- C. 80 g
- D. 10 g
Explanation: The molar mass is 23 + 16 + 1, that is 40 g per mole, so half a mole has a mass of 20 g.
Correct answer: 20 g- A. 6.02 x 10^23
- B. 4.21 x 10^24
- C. 4.214 x 10^24
- D. 98
Explanation: One molecule contains 2 + 1 + 4, that is 7 atoms, so one mole contains 7 x 6.02 x 10^23, which is 4.214 x 10^24 atoms.
Correct answer: 4.214 x 10^24- A. CH2O
- B. C2H4O2
- C. C3H6O3
- D. C6H12O6
Explanation: The empirical formula mass is 12 + 2 + 16, that is 30, and 180 divided by 30 gives 6, so every subscript is multiplied by six to give…
Correct answer: C6H12O6- A. 27.3 per cent
- B. 12 per cent
- C. 44 per cent
- D. 72.7 per cent
Explanation: The molar mass is 12 + 32, that is 44, so the carbon fraction is 12 divided by 44 multiplied by 100, giving 27.3 per cent.
Correct answer: 27.3 per cent- A. is present in the largest amount by mass
- B. is completely used up first and so determines the amount of product formed
- C. has the highest molar mass
- D. remains unreacted at the end
Explanation: The reaction stops when one reactant runs out, so that reactant fixes the maximum yield no matter how much of the others is present.
Correct answer: is completely used up first and so determines the amount of product formed- A. nitrogen, because it has the larger molar mass
- B. neither, because both are used up exactly
- C. hydrogen, because 3 moles would be needed to react with 1 mole of nitrogen
- D. nitrogen, because fewer moles of it are present
Explanation: The equation demands three moles of hydrogen for every mole of nitrogen, so 1 mole of nitrogen would need 3 moles of hydrogen and only 2…
Correct answer: hydrogen, because 3 moles would be needed to react with 1 mole of nitrogen- A. 2 moles of hydrogen
- B. 3 moles of oxygen
- C. nothing, both are exactly consumed
- D. 1 mole of oxygen
Explanation: Four moles of hydrogen require only two moles of oxygen, so hydrogen is limiting and 3 minus 2, that is 1 mole of oxygen, remains…
Correct answer: 1 mole of oxygen- A. the maximum mass of product calculated from the balanced equation and the limiting reactant
- B. the mass of product actually obtained in the laboratory
- C. always equal to the mass of the limiting reactant
- D. the mass of the excess reactant left over
Explanation: Theoretical yield is a calculation, assuming the reaction goes to completion with no losses and no side reactions, and it is the standard…
Correct answer: the maximum mass of product calculated from the balanced equation and the limiting reactant- A. 125 per cent
- B. 80 per cent
- C. 5 per cent
- D. 20 per cent
Explanation: Percentage yield is actual divided by theoretical multiplied by 100, so 20 divided by 25 multiplied by 100 gives 80 per cent.
Correct answer: 80 per cent- A. some product is lost during filtration and transfer
- B. side reactions produce unwanted products
- C. the balanced equation was written incorrectly
- D. the reaction is reversible and does not go to completion
Explanation: Physical losses, competing side reactions and reversibility are all genuine reasons why a real yield falls short.
Correct answer: the balanced equation was written incorrectly- A. 100 g
- B. 44 g
- C. 40 g
- D. 56 g
Explanation: The equation shows a one to one ratio, so 1 mole of CaCO3 gives 1 mole of CaO, whose molar mass is 40 + 16, that is 56 g.
Correct answer: 56 g- A. 44 g per mole
- B. 28 g per mole
- C. 12 g per mole
- D. 32 g per mole
Explanation: Adding one carbon at 12 and two oxygens at 16 each gives 12 + 32, that is 44 g per mole.
Correct answer: 44 g per mole- A. the mass in grams of one atom of the element
- B. the average mass of its atoms compared with one twelfth the mass of a carbon 12 atom
- C. the number of protons in its nucleus
- D. always a whole number
Explanation: Relative atomic mass is a ratio, so it has no units, and it is an average weighted by the natural abundance of the isotopes.
Correct answer: the average mass of its atoms compared with one twelfth the mass of a carbon 12 atom- A. 1000 g of solvent
- B. one litre of solvent
- C. one cubic decimetre of solution
- D. one mole of solvent
Explanation: Molarity refers to the total volume of the final solution, not to the volume of solvent used, which is why a standard solution is made up…
Correct answer: one cubic decimetre of solution- A. 1 mole of helium gas
- B. 1 mole of oxygen gas, O2
- C. 1 mole of water, H2O
- D. 1 mole of ammonia, NH3
Explanation: Every sample contains one mole of molecules, so the answer depends on the number of atoms in each molecule: helium has one, oxygen two…
Correct answer: 1 mole of ammonia, NH3Fundamental Concepts of Chemistry MCQs: common questions
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