In a soda acid fire extinguisher, concentrated sulfuric acid reacts with sodium hydrogen carbonate to produce carbon dioxide, sodium sulfate and water. How many moles of sodium hydrogen carbonate are produced from a reaction of 0.4 moles of sulfuric acid?

Question

Write the balanced equation first.
2NaHCO3 + H2 SO4 >>> Na2 SO4 + 2H2 O +2CO2

Answer 1

Please read your post and note how ridiculous it reads. The answer is that it produces zero mols NaHCO3. You start with NaHCO3.
Let's suppose you asked instead to calculate the mols NaHCO3 NEEDED to react with 0.4 mols H2SO4.
That's the old trick of using the coefficients in the balanced equation to convert what you have into what you want.
0.4 mol H2SO4 x (2 mols NaHCO3/1 mol H2SO4) = 0.4 x 2/1 = 0.8 mols NaHCO3 needed. If it is some other conversion you need it is done the same way.