Final answer:
The number of CO2 molecules produced in a reaction is calculated through stoichiometry, using the balanced chemical equation and the molar ratios of the reactants and products. For 0.75 moles of propane combusted, the equation indicates three moles of CO2 are produced per mole of propane, leading to 2.25 moles of CO2; multiplying this by Avogadro's number gives the total number of molecules.
Step-by-step explanation:
The number of carbon dioxide molecules formed from a reaction mixture is determined through stoichiometry, which involves balancing the chemical equation and using molar ratios. For example, when propane is combusted, the chemical equation is C3H8 + 5 O2 → 3 CO2 + 4 H2O. If you start with 0.75 moles of propane, the stoichiometric ratio of propane to carbon dioxide is 1:3, meaning that for every mole of propane, three moles of carbon dioxide are produced. Therefore, 0.75 moles of propane would result in 2.25 moles of CO2, and since one mole of any substance contains Avogadro's number of molecules (6.022 x 1023), you would multiply 2.25 by Avogadro's number to find the actual number of CO2 molecules produced.