I need help with this question it's science

How many liters of hydrogen gas will be produced at stp from the reaction of 7.179×10^23 atoms of magnesium with 54.219g of phosphoric acid (h3po4) the equation is 3mg + 2h3(> mg(po4)2+3h2

Use the table to identify the phase and phase changes of the elements under the given conditions. write the name of the substance, phase, or phase change

If 90.0 grams of ethane reacted with excess chlorine,how many grams of dicarbon hexachloride would form