How is stoichiometry used to calculate the mass of a substance?
o
a. unit conversion factors are used to convert between units of
grams and moles.
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b. oxidation numbers are used to convert from moles of one
molecule to moles of another molecule.
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c. subscripts in chemical formulas are used to calculate amounts of
substances.
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d. percent contributions are used to convert between molar mass
and mass.
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A. Unit conversion factors are used to convert between units of

grams and moles.

Explanation:In stoichiometry mass of a substance is calculated from the inter-conversion between moles and grams using conversion factors.That is, to calculate the mass of a compound or an element in a chemical equation we multiply the number of moles by the molar mass of the compound.Moles can be calculated from the mole ratio of reactants and products involved or by dividing mass of a compound by the molar mass.