Chemistry Clarity · chemistryclarity.com

Balancing Chemical Equations: Flashcards

Revise conservation of mass, coefficients vs subscripts, counting atoms and balancing equations.

10 cardsBeginner

10 cards

  1. Question
    What does it mean for a chemical equation to be balanced?
    Answer

    Every element has the same number of atoms on both sides of the arrow.

  2. Question
    Which law requires equations to be balanced?
    Answer

    The law of conservation of mass: atoms are rearranged, never created or destroyed.

  3. Question
    When balancing, do you change coefficients or subscripts?
    Answer

    Coefficients only. Changing a subscript changes the substance.

  4. Question
    How many O atoms are in 3 COX2\ce{3CO2}?
    Answer

    3 × 2 = 6

  5. Question
    How many O atoms are in Ca(NOX3)X2\ce{Ca(NO3)2}?
    Answer

    2 × 3 = 6

  6. Question
    Balance: HX2+OX2→HX2O\ce{H2 + O2 -> H2O}
    Answer

    2 HX2+OX2→2 HX2O\ce{2H2 + O2 -> 2H2O}

  7. Question
    Balance: CHX4+OX2→COX2+HX2O\ce{CH4 + O2 -> CO2 + H2O}
    Answer

    CHX4+2 OX2→COX2+2 HX2O\ce{CH4 + 2O2 -> CO2 + 2H2O}

  8. Question
    Balance: NX2+HX2→NHX3\ce{N2 + H2 -> NH3}
    Answer

    NX2+3 HX2→2 NHX3\ce{N2 + 3H2 -> 2NH3}

  9. Question
    Which elements are usually best left until last when balancing?
    Answer

    Hydrogen and oxygen, and any element on its own such as OX2\ce{O2} or Fe\ce{Fe}.

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

    The ratio of particles (and of moles) that react and form. They do not give the ratio of masses.