Many fireworks mixtures depend on the highly energetic combustion of magnesium, in which the heat causes the oxide to become incandescent and to give out a bright white light. The color of the light can be changed by including nitrates and chlorides of elements that have emissions in the visible region of their spectra. Barium nitrate is often added to produce a yellow-green color. The excited barium ions generate light of wavelength 487 nm, 524 nm, 543 nm, 553 nm, and 578 nm. For each case, calculate

(a) The change in energy (in electronvolts) of a barium atom and

(b) The molar change in energy (in kilojoules per mole).