Trichloroethylene, a widely used degreasing solvent for machine parts is produced in a two-step reaction sequence. Ethylene is first chlorinated to yield tetrachloroethane, which is dehydrochlorinated to form trichloroethylene. C2H4 (g) + Cl2 (g) ? C2H2C14 (1) + H2 (g): ?H°? = —385.76 kJ/mol C2H2C14 (l) ? C2HCl3 (l) + HC1 (g)
The standard heat of formation of liquid trichloroethylene is —276.2 kJ/mol
(a) Use the given data and tabulated standard heats of formation of ethylene and hydrogen chloride to calculate the standard heat of formation of tetrachloroethane and the standard heat of the second reaction.
(b) Use Hess’s law to calculate the standard heat of the reaction C2H4 (g) + 2 C12 (g) — C2HCI3 (l) + H2 (g) + HCI (g)
(c) If 300 mol/h of C2HC13 (l) is produced in the reaction of part (b) and the reactants and products are all at 25°C and I atm, how much heat is evolved or absorbed in the process? (Assume Q = ?H)