Find the number of atoms of lead in 30.04 moles of leads

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.

Acompound has a molecular weight of 12.124 atomic mass units and the empirical formula c3h40. what is the molecular formula of the compound?

12. calculate the hydroxide ion concentration of a solution with ph = 3.25. show all calculations leading to an answer