A 0.45g sample of mineral ore is analised for chromium and found to contain 0.560mg Cr2O3. Express the concentration of Cr2O3 in the sample as a) percent B)parts the thousands C)parts per million D) parts per billion

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?