The following mechanism has been proposed for the gas-phase reaction of chloroform (CHCl3) and chlorine:

Step 1: Cl2(g)⇌2Cl(g)(fast)
Step 2: Cl(g)+CHCl3(g)→HCl(g)+CCl3(g)(slow)
Step 3: Cl(g)+CCl3(g)→CCl4(fast)

What is the overall rate constant?