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Stoichiometry: Flashcards

Revise mole ratios and the grams → moles → moles → grams method.

9 cardsIntermediate

9 cards

  1. Question
    What is stoichiometry?
    Answer

    Using a balanced chemical equation to calculate the amounts of substances that react or are produced.

  2. Question
    What do the coefficients in a balanced equation tell you?
    Answer

    The mole ratio between the substances (not the mass ratio).

  3. Question
    What are the three steps of a stoichiometry calculation?
    Answer

    1. Convert what you know to moles. 2. Multiply by the mole ratio from the balanced equation. 3. Convert moles to what is asked for.

  4. Question
    How do you write the mole ratio so it isn't upside down?
    Answer

    Want ÷ have: (coefficient of the substance you want) ÷ (coefficient of the substance you know).

  5. Question
    In 2 HX2+OX2→2 HX2O\ce{2H2 + O2 -> 2H2O}, how many moles of OX2\ce{O2} react with 4 mol of HX2\ce{H2}?
    Answer

    4×12=24 \times \dfrac{1}{2} = 2 mol of OX2\ce{O2}

  6. Question
    In NX2+3 HX2→2 NHX3\ce{N2 + 3H2 -> 2NH3}, how many moles of NHX3\ce{NH3} form from 3.0 mol of HX2\ce{H2}?
    Answer

    3.0×23=2.03.0 \times \dfrac{2}{3} = 2.0 mol of NHX3\ce{NH3}

  7. Question
    Why must the equation be balanced before you calculate?
    Answer

    Only a balanced equation gives the correct mole ratio. An unbalanced one gives the wrong answer.

  8. Question
    Can you convert grams of A directly into grams of B using the coefficients?
    Answer

    No. The equation connects moles to moles. Go grams → moles → moles → grams.

  9. Question
    How can you check a stoichiometry answer?
    Answer

    Mass is conserved: the total mass of reactants used equals the total mass of products formed.