A. calculate the mass percent of nahco3 based on the manufacturer's list of ingredients: 325mg aspirin, 1000 mg citric acid, 1916 mg nahc03 .

The mass percent of NaHCO3 can be calculated by dividing the mass of NaHCO3 by the total mass of the compound and then multiplying the quotient by 100 to get the percentage.

mass % of NaHCO3 = (mass of NaHCO3 / total mass) * 100

Now, we have:
mass of NaHCO3 = 1916 mg
total mass = 325 + 1000 + 1916 = 3241 mg

Substitute with these numbers in the equation to get the mass percentage as follows:
mass  % = (1916/3241) * 100 = 59.11755631%

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