Asubstance with a definite shape and volume is a phase of matter

Plz choose one of the compounds from the table and explain how you know the numbers of atoms in your formula. is it possible for two different compounds to be made from the exact same two elements? why or why not? with a limited number of elements (less than 120 are known), does this mean we also have a small number of compounds or do we have a large number of compounds in this world?

Needthe meter is the standard unit for: 1) height 2) length 3) weight 4) mass

What is the overall order of reaction for rate = k[no2]2 ? second order 3/2 order third order zero order none of the listed answers are correct