In balancing equations, why do i put a 3 before reactant h?

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.

How many grams are in 68.2 molecules of br2?

State the effect on the concentration of the clo- ion when there is a decrease in the concentration of the oh- ion