the second-order rate constant for the following gas-phase reaction is 0.046 1/m⋅s. we start with 0.123 mol c2f4 in a 2.62 liter container, with no c4f8 initially present. c2f4 ⟶ 1/2 c4f8 what will be the concentration of c2f4 after 1.38 hours? enter to 4 decimal places.