When silver coins are found in ancient shipwrecks, they are coated with a black crust. what question could you ask to you decide whether the silver underwent a chemical change or a physical change? explain.

Nitrogen dioxide decomposes according to the reaction 2 no2(g) ⇌ 2 no(g) + o2(g) where kp = 4.48 × 10−13 at a certain temperature. if 0.70 atm of no2 is added to a container and allowed to come to equilibrium, what are the equilibrium partial pressures of no(g) and o2(g)