mixed stoichiometry

Question

How many moles of hydrogen carbonate need to decompose to produce 2.25 x 10^24 molecules of carbon dioxide if water is the only other product?

Answer 1

The molar ratio of hydrogen carbonate ion (HCO₃^-) to carbon dioxide would be 1:1. And knowing that there are 6.023 x 10²³ molecules per mole (of anything),the problem could be solved as follows:

(1 mol HCO₃^-/1 mol CO₂) (1 mol CO₂/6.023 x 10²³ molecules CO₂) (2.25 x 10²⁴ molecules CO₂)

= 3.74 moles of HCO₃^-