Rate Law Problem?

Kinetic studies of hydrogen halide formation show that the rate law for HBr formation is the following. H2(g) + Br2(g) ---> 2 HBr (g), rate = k[H2][Br2]^1/2 I. Br2(g) ---> 2 Br(g) [fast] Br(g) + H2(g) ---> HBr(g) + H(g) [slow] H(g) + Br(g) ---> HBr(g) [fast] II. H2(g) +... show more Kinetic studies of hydrogen halide formation show that the rate law for HBr formation is the following.

H2(g) + Br2(g) ---> 2 HBr (g), rate = k[H2][Br2]^1/2

I. Br2(g) ---> 2 Br(g) [fast]
Br(g) + H2(g) ---> HBr(g) + H(g) [slow]
H(g) + Br(g) ---> HBr(g) [fast]

II. H2(g) + Br2(g) ---> 2 HBr(g)

III. H2(g) ---> 2 H(g) [fast]
H(g) + Br2(g) ---> HBr(g) + Br(g) [slow]
Br(g) + H(g) ---> HBr(g) [fast]

IV. none of these

Which of the above mechanisms, if any, is consistent with the rate law? (choose all that apply)
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