Let the rate law be Rate=k[CH3COCH3]x[Br2]y[H+]z.
Comparing experiment 1 and 2: When [Br2] is doubled (0.05 M to 0.10 M) while keeping other concentrations constant, the rate remains unchanged (5.7×10−5 M s−1). Thus, the order with respect to Br2 is 0 (y=0).
Comparing experiment 2 and 3: When [H+] is doubled (0.05 M to 0.10 M) keeping other concentrations constant, the rate is approximately doubled (from 5.7×10−5 to 1.2×10−4≈1.14×10−4). Thus, the order with respect to H+ is 1 (z=1).
Comparing experiment 1 and 4: [CH3COCH3] is increased by 4/3 times (0.30 to 0.40), [Br2] is unchanged, and [H+] is increased by 4 times (0.05 to 0.20). The rate becomes 5.7×10−53.1×10−4≈5.44 times the initial rate.
Based on the previously determined orders, the expected new rate would be proportional to the changes:
Rate4=Rate1×(0.300.40)x×(0.050.20)1
3.1×10−4=5.7×10−5×(34)x×4
(34)x=5.7×10−5×43.1×10−4=22.83.1≈1.36
Since 34≈1.33, we get x=1.
Therefore, the overall rate equation is Rate=k[CH3COCH3]1[Br2]0[H+]1=k[CH3COCH3][H+].