Acetylene is hydrogenated to form ethane

Acetylene is hydrogenated to form ethane. The feed to the reactor contains 1.50mol H2/mol C2H2.
(a) Calculate the stoichiometric reactant ratio (mol H2 react/mol C2H2 react) and the yield ratio (k mol C2H6 formed/k mol H2 react).
(b) Determine the limiting reactant and calculate the percentage by which the other reactant is in excess.
(C) Calculate the mass feed rate of hydrogen (kg/s) required to produce 4 x 106 metric tons of ethane per year, assuming that the reaction goes to completion and that the process operates for 24 hours a day, 300 days a year.
(d) There is a definite drawback to running with one reactant in excess rather than feeding the reactants in stoichiometric proportion. What is it?