A certain first order reaction has a half-life of 54.3 s. How long will it take (in s) for the reactant concentration to decrease from 6.50 M to 2.27 M

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?

The molar mass of iron(fe) is 55.8 g/mol. what is the mass in grams of 2.25 moles of iron?

A2-kg bowling ball is 1 meter off the ground on a post when it falls. just before it reaches the ground,its traveling 4.4 m/s. assuming that there is no air resistant, which statement is true a. the initial potential energy is less then the final kinetic energy b. the mechanical energy is not conserved c. the mechanical energy is conserved d. the initial potential energy is greater than the final kinetic energy