Which compound has the greatest molecular mass?

CO2

H2O

Pb2

NH4

C) the increase in atmospheric pressure pushes the walls of the balloon outward thus making it  is the answer.hope i you.

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).