. If 17.4 grams of methane (CH) are reacted with excess oxygen in a complete combustion reaction at STP, how many liters of carbon dioxide will be formed?
(molar mass of methane = 16.05g/mol)

CH4 + 2O2->CO2 + 2H20

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?