In this reaction, Copper is the element being oxidized because it is losing electrons. It starts with a neutral charge (0) and ends up with a 6+ charge. Because its charge is increasing, it is being oxidized (losing electrons).
Molar mass of Na2SO4*10H2O is 322.1949 g/mol
Is this a question? if so please elaborate.
Molecules do not have enough kinetic energy to overcome the intermolecular bonds.