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Chemistry: Chemical Reactions & Stoichiometry Flashcards

7 cards from real AP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. How many moles of O2 are required to completely combust 2 mol of C3H8 (propane)?

    Answer: 10 mol

    Balanced equation C3H8 + 5O2 -> 3CO2 + 4H2O needs 5 mol O2 per mol propane, so 2 mol needs 10 mol.

  2. What is the molar mass of calcium phosphate, Ca3(PO4)2?

    Answer: 310.18 g/mol

    3(40.08) + 2(30.97) + 8(16.00) = 310.18 g/mol.

  3. In the reaction 2Al + 3Cl2 -> 2AlCl3, if 4 mol Al react, how many mol AlCl3 form?

    Answer: 4 mol

    The Al:AlCl3 ratio is 2:2 (1:1), so 4 mol Al yields 4 mol AlCl3.

  4. Which quantity equals one mole of any substance?

    Answer: 6.022 x 10^23 representative particles

    A mole is defined as 6.022 x 10^23 (Avogadro's number) of representative particles.

  5. What is the percent by mass of nitrogen in NH4NO3?

    Answer: 35.0%

    Two N atoms (28.02 g) over molar mass 80.06 g gives about 35.0%.

  6. A reaction produces 18.0 g of water from an actual yield experiment whose theoretical yield is 24.0 g. What is the percent yield?

    Answer: 75.0%

    Percent yield = (18.0/24.0) x 100 = 75.0%.

  7. How many atoms of oxygen are present in 0.500 mol of CO2?

    Answer: 6.02 x 10^23

    0.500 mol CO2 has 1.00 mol O atoms = 6.02 x 10^23 atoms.