Final answer:
The coefficient 2 in front of H2O2 indicates that there are 2 molecules of hydrogen peroxide. Each molecule of H2O2 has 2 hydrogen atoms and 2 oxygen atoms, so 2 molecules contain a total of 4 hydrogen atoms and 4 oxygen atoms.
Step-by-step explanation:
The question "how many molecules are in 2H2O2" refers to a quantity of a chemical compound, specifically hydrogen peroxide. When we talk about molecules, we need to understand that the coefficient in front of a chemical formula indicates the number of molecules. Therefore, when we see the coefficient 2 in front of H2O2, it indicates that we have 2 molecules of hydrogen peroxide.
In chemical equations, coefficients are used to balance the molar amounts of reactants and products at the molecular level. For example, the balanced chemical equation 2H2 + O2 → 2H2O can be read as "two moles of hydrogen react with one mole of oxygen to produce two moles of water," where the coefficients represent molar amounts, not individual molecules.
Using conversion factors in stoichiometry, the coefficients can also tell us about the number of atoms within the molecules. If we have 2 molecules of H2O2, we have 4 hydrogen atoms and 4 oxygen atoms because each molecule of H2O2 contains 2 hydrogen atoms and 2 oxygen atoms. Hence, in 2 molecules of H2O2, there are a total of 4 hydrogen atoms and 4 oxygen atoms.