How many isotopes of hydrogen exist in nature?

Describe in detail the melting point behavior of the 80: 20 benzoic acid-mandelic acid mixture

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)

At element makes up all organic compounds?