Name:
Reaction Order and Rate Law Expression Worksheet
1. Given the following equations and experimental data, write the correct rate law equation
including the value for the rate constant and indicate the overall order of the reaction.
A) A2 + B2  2 AB
Exp #
[A2]
[B2]
Rate
1
2
3
4
0.0010
0.0010
0.0010
0.0030
0.0010
0.0020
0.0040
0.0040
(mole L-1 s-1)
0.010
0.020
0.040
0.36
For A2 compare 4 & 5: [A2] x2 rate x4=22 , 2nd order for A2
For B2 compare 1 & 2: [B2] x2 rate x2=21 , 1st order for B2
2
r  k [ A ] [B ]
2
2
r
k
2
reaction order = 3
[ A2 ] [ B2 ]
k
0.010
(0.0010) 2 (0.0010)
k  1.0 x10 7
2
r  1.0 x10 7 [ A ] [ B ]
2
2
B) C + D  E
Exp #
1
2
3
[C]
0.1
0.1
0.3
[D]
Rate
0.01
0.04
0.04
(mole L-1 s-1)
0.02
0.08
0.08
For C compare 4 & 5: [C] x2 rate x1=20 , 0th order for C
For D compare 1 & 2: [D] x2 rate x2=21 , 1st order for D
r  k [ D]
k
r
[D]
k
0.020
(0.010)
k  2.0 x10 3
r  2.0 x10 3 [ D]
reaction order = 1
C) F + G  H
Exp #
1
2
3
4
[F]
0.01
0.03
0.1
0.1
[G]
Rate
0.4
0.4
0.2
0.4
(mole L-1 s-1)
0.02
0.06
0.10
0.20
For F compare 4 & 5: [F] x2 rate x2=21 , 1st order for F
For G compare 1 & 2: [G] x2 rate x2=21 , 1st order for G
r  k [ F ] [G]
r
k
reaction order = 2
[ F ] [G]
0.020
(0.010)(0.40)
k  5.0
k
r  5.0[ F ] [G]
D) C + D  E
Exp #
1
3
4
5
[C]
0.1
0.1
0.1
0.2
[D]
Rate
0.01
0.03
0.04
0.04
(mole L-1 s-1)
0.02
0.18
0.32
1.28
For C compare 4 & 5: [C] x2 rate x4=22 , 2nd order for C
For D compare 1 & 2: [D] x2 rate x4=22 , 2nd order for D
2
2
r  k [C ] [ D]
k
r
2
reaction order = 4
2
[C ] [ D]
k
0.020
(0.10) 2 (0.010) 2
k  2.0 x10 4
2
2
r  2.0 x10 4 [C ] [ D]
E) F + G  H
Exp #
1
2
3
4
[F]
0.01
0.02
0.1
0.1
[G]
Rate
0.4
0.4
0.2
0.4
(mole L-1 s-1)
0.02
0.16
5
20
For F compare 1 & 2: [F] x2 rate x8=23 , 3rd order for F
For G compare 1 & 2: [G] x2 rate x4=22 , 2nd order for G
3
2
r  k [ F ] [G ]
k
r
3
2
[ F ] [G]
k
reaction order = 5
0.020
(0.010) 3 (0.40) 2
k  1.3 x10 5
3
2
r  1.3 x10 5 [ F ] [G ]
2. The initial rate of the reaction: BrO3-(aq) + 5 Br-(aq) + 8 H+(aq) ----> 3 Br2(l) + H2O(l)
Has been measured at the reactant concentrations shown (in mol/L):
Trial
[BrO3-]
[Br-]
[H+]
Initial rate
(mol/Ls)
1
0.10
0.10
0.10
8.0 x 10-4
2
0.20
0.10
0.10
1.6 x 10-3
3
0.10
0.20
0.10
1.6 x 10-3
4
0.10
0.10
0.20
3.2 x 10-3
A) Determine the rate law equation including the k value.
For BrO3- compare 1 & 2: [BrO3-] x2 rate x2=21 , 1st order for BrO3For Br- compare 1 & 2: [Br-] x2 rate x2=21 , 1st order for BrFor H+ compare 1 & 4, [H+] x2 rate x4=22 , 2nd order for H+
2
r  k [ BrO  ] [ Br  ][ H  ]
3
r
k
2
[ BrO3 ] [ Br  ][H  ]
0.020
k
(0.10)(0.10)(0.10) 2
k  2.0 x10 2
r  2.0 x10 2 [ BrO  ] [ Br  ][ H  ]
3
2
B) Determine the initial rate (in mol/Ls) if all three concentrations are 0.20 mol/L.
r=2.0x102[BrO3-][Br-][H+]2
r=2.0x102[0.20][0.20][0.20]2
r=0.32 mol/Ls