A 6.0 mol sample of C3H8 (g) and a 20. mol sample of Cl2 (g) are placed in a previously evacuated vessel, where they react according to the equation above. After one of the reactants has been totally consumed, how many moles of HCl (g) have been produced? (A) (B) (C) (D) 4.0 mol 8.0 mol 20. mol 24 mol

According to the provided equation:

1 mole of propane reacts with 4 moles Cl₂ to give 4 moles HCl

so 6 moles of propane react completely with 24 moles Cl₂ but we have only 20 moles Cl₂ so it is the limiting reactant:

4 moles Cl₂ - - > 4 moles HCl

20 moles Cl₂ - - - >? moles HCl

so the correct answer is 20 moles HCl