Baking soda (nahco3) is an active ingredient in some antacids. determine the percent composition of oxygen in baking soda.

Assuming the question is asking for percent composition by mass,

The molar mass of sodium bicarbonate is:

22.990 + 1.008 + 12.011 + 3*15.999 = 84.006 g/mol

The molar mass of 3 oxygen atoms is:

3*15.999 = 47.997 g/mol

The percentage composition by mass is:

47.997/84.006 * 100% = 57.1% (3 s. f.)