If the initial concentration of SO2Cl2 is 1.00 M, how long will it take for the concentration to decrease to 0.72 M?
The decomposition of SO2Cl2 is first order in SO2Cl2 and has a rate constant of 1.36×10^(-4) s−1 at a certain temperature.
The decomposition of SO2Cl2 is first order in SO2Cl2 and has a rate constant of 1.36×10^(-4) s−1 at a certain temperature.
Steve4Physics
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For a first order reaction the concentration decreases exponentially according to:
C(t) = C₀e^(-kt)
With the given values:
0.72 = 1.00e^(-1.36x10⁻⁴t)
e^(-1.36x10⁻⁴t) = 0.72
Take natural logs of both sides:
-1.36x10⁻⁴t = ln(0.72)
. . . . . . . . . = -0.3285
t = 0.3285 /(1.36x10⁻⁴)
. = 2415s
Best to round to 2 sig. figs as the final concentration (0.72M) is only 2 sig. figs.
t = 2400s to 2 sig. figs. (about 40 minutes)