17 (a) What safety precaution is usually taken in storing acetylene? (b) How much excess H2 would have to be used in a gas-phase ethylene polymerization process (n C2H4(C2H4)n,HR=25kcal/ mole) to have the adiabatic temperature rise not exceed 300C ? List at least two reasons why isobutane is a preferred diluent instead of H2 to prevent thermal runaway in this reaction