Propane has the formula c3h8. if a sample of propane contains 0.20 moles of c, how many moles of h are present?

Solving this problem only requires the knowledge of stoichiometry. We are given the compound propane C3H8. From the chemical formula, we can see that for every 3 moles of C, there are 8 moles of H. Therefore:

moles of H = 0.20 moles C * (8 moles H / 3 moles C)

moles of H = 0.53 moles H

- "the choice that is not an indicator of a chemical change is "state of matter changes". more common than not, chemical reactions produce energy in the form of light or heat. along with energy, they also produce a new substance called the product that could be in any state of matter (solid, gas, or liquid)."

if you mean hydrogen and oxygen then water is the product