if 6 moles of H2 react with 6 moles of Cl2 to form HCl, calculate the work done(in joule) against a pressure of 1.0 atm. What is the internal energy

if 6 moles of H2 react with 6 moles of Cl2 to form HCl, calculate the work done(in joule) against a pressure of 1.0 atm. What is the internal energy for this reaction? assume the reaction goes to completion