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Fundamentals of Chemistry MCQs for MDCAT Practice

Chemistry section, Fundamentals of Chemistry chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

The bank has 1,149 active questions on this chapter. Your first 500 practice attempts are free, and every attempt includes a worked explanation.

  1. Question 1
    In a vessel 10g N2, 10g H2 and 10g O2 are present. Which one will have least number of atoms?
    • H2
    • N2
    • O2 (correct answer)
    • Both H2 and N2
    Correct answer: C
    This question tests your ability to calculate the number of atoms from mass and molar mass, emphasizing the importance of molecular structure.
  2. Question 2
    The molecular mass of a compound is 60, and its empirical formula is CH2O. What will be the molecular formula for a compound?
    • C6H12O6
    • C2H4O2 (correct answer)
    • C2H6O2
    • C2H8O2
    Correct answer: B
    Determine the molecular formula from the empirical formula and molecular mass by finding the whole-number multiple relating them.
  3. Question 3
    How many total number of electrons are present in 48 g of Mg2+? (NA = 6.023 x 1023)
    • 24 NA
    • 2 NA
    • 20 NA (correct answer)
    • 1 NA
    Correct answer: C
    Calculate total electrons in a given mass of an ion by relating moles, Avogadro's number, and atomic structure.
  4. Question 4
    In this question you should assume air contains 20% oxygen. What is the minimum volume of air required to ensure complete combustion of 10 cm3 of butane gas, under room conditions?
    • 14 cm3.
    • 65 cm3.
    • 310 cm3.
    • 325 cm3. (correct answer)
    Correct answer: D
    Stoichiometry of combustion reactions is key to determining reactant volumes, especially when considering gas mixtures like air.
  5. Question 5
    Efficiency of chemical reaction can be checked by calculating
    • Actual yield
    • Theoretical yield
    • Percentage yield (correct answer)
    • Amount of the reactant unused
    Correct answer: C
    Percentage yield quantifies a reaction's efficiency by comparing actual product obtained to the maximum possible.
  6. Question 6
    If we are given the mass of a substance, we can calculate _____ of other substances with the help of a balanced chemical equation.
    • Mass
    • Volume
    • Moles
    • All of these options are correct (correct answer)
    Correct answer: D
    Stoichiometry allows calculation of mass, volume, and moles of substances using a balanced chemical equation and a known mass.
  7. Question 7
    Which of the following compound contains the highest percentage by mass of nitrogen?
    • NH3
    • N2H4 (correct answer)
    • NO
    • NH4OH
    Correct answer: B
    Calculate the mass percentage of nitrogen in each compound to determine which has the highest nitrogen content by mass. Hydrazine (N2H4) has the highest nitrogen percentage.
  8. Question 8
    Which contains more atoms?
    • 7 gram Mg
    • 8 gram Na (correct answer)
    • 9 gram Al
    • All same
    Correct answer: B
    To determine which mass contains more atoms, calculate the moles of each element and then multiply by Avogadro's number. Option B has the highest number of moles and thus atoms.

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