Urgenttt help will be much appreciated

The name of the ion, s2-, is: sulfurous ion sulfide ion sulfur ion sulfate ion

Athe top of a hill, an athlete on a skateboard has x joules of mechanical energy. how much mechanical energy will she have at the bottom of the hill? ignore the effects of friction.

Calculate the mass of 0.750 mol of the following substance. na3po4. , i'm not quite sure on how to set up the problem to solve! : (