A mass of 18.1 g of an element is known to contain 4.22x 1023 atoms. What is the atomic mass of the element?

The enthalpy of formation of water is -285.8 kj/mol. what can be inferred from this statement?

Calculate the change in entropy if br2(l) is converted to br2(g). s° for br2(l) = 152.2 j/(mol•k) s° for br2(g) = 245.5 j/(mol•k) s° for br(g) = 175.0 j/(mol•k)

How could a student test the effect of removing heat from a gas that is stored in a sealed container? what must occur in order for matter to change states?