What is the mass percent of oxygen in sodium bicarbonate (nahco3)?

The answer is 57.14%.

First we need to calculate molar mass of NaHCO3. Molar mass is mass of 1 mole of a substance. It is the sum of relative atomic masses, which are masses of atoms of the elements.

Relative atomic mass of Na is 22.99 g
Relative atomic mass of H is 1 g
Relative atomic mass of C is 12.01 g
Relative atomic mass of O is 16 g.

Molar mass of NaHCO3 is:
22.99 g + 1 g + 12.01 g + 3 · 16 g = 84 g

Now, mass of oxygen in NaHCO3 is:
3 · 16 g = 48 g

mass percent of oxygen in NaHCO3:
48 g ÷ 84 g · 100% = 57.14%

Therefore, the mass percent of oxygen in sodium bicarbonate is 57.14%.