a) The Overall Equation is
ClO⁻(aq) + I⁻(aq) → Cl⁻(aq) + IO⁻(aq)
b) The intermediates include
HClO(aq)
OH⁻(aq)
HIO(aq)
H₂O(l)
c) Step 1
rate = k [ClO⁻] [H₂O]
Moleculiarity = 2, Bimolecular
Step 2
rate = k [I⁻] [HClO]
Moleculiarity = 2, Hence, it is Bimolecular
Step 3
rate = k [OH⁻][HIO]
Moleculiarity = 2, Hence, it is Bimolecular too.
d) No, this mechanism isn't consistent with the actual rate law.
Explanation:
(1) ClO⁻(aq) + H₂O(l) ⇌ HClO(aq) + OH⁻(aq) [fast]
(2) I⁻(aq) + HClO(aq) → HIO(aq) + Cl⁻(aq) [slow]
(3) OH⁻(aq) + HIO(aq) → H₂O(l) + IO⁻(aq) [fast]
a) For the overall reaction, summing the elementary reactions up.
ClO⁻(aq) + H₂O(l) + I⁻(aq) + HClO(aq) + OH⁻(aq) + HIO(aq) → HClO(aq) + OH⁻(aq) + HIO(aq) + Cl⁻(aq) + H₂O(l) + IO⁻(aq)
We then eliminate those that appear on both sides of the eqn. Those ones are the intermediates.
HClO(aq)
OH⁻(aq)
HIO(aq)
H₂O(l)
Then we have
ClO⁻(aq) + I⁻(aq) → Cl⁻(aq) + IO⁻(aq)
Hence, this is the overall equation.
b) Like we pointed out in (a), all those that appeared on both sides of the overall equation, are intermediates.
HClO(aq)
OH⁻(aq)
HIO(aq)
H₂O(l)
c) Moleculiarity and Rate Law for each step
Moleculiarity is expressed as the number of molecules that react in the elementary reaction. It is simply the sum of their coefficients in a balanced elementary equation.
Step 1
rate = k [ClO⁻] [H₂O]
Moleculiarity = 2, Bimolecular.
Step 2
rate = k [I⁻] [HClO]
Moleculiarity = 2, Hence, it is Bimolecular
Step 3
rate = k [OH⁻][HIO]
Moleculiarity = 2, Hence, it is Bimolecular too.
d) We first try to write the overall rate law from the elementary steps given
(1) ClO⁻(aq) + H₂O(l) ⇌ HClO(aq) + OH⁻(aq) [fast]
(2) I⁻(aq) + HClO(aq) → HIO(aq) + Cl⁻(aq) [slow]
(3) OH⁻(aq) + HIO(aq) → H₂O(l) + IO⁻(aq) [fast]
The slow step is usually the rate determining step
So, from step 2,
Rate = k [I⁻] [HClO]
But from step 1,
rate = k [ClO⁻] [H₂O]
But k₁ [ClO⁻] [H₂O] = k₂ [HClO] [OH⁻]
[HClO] = (k₁/k₂) [ClO⁻] [H₂O]/[OH⁻]
Rate = K [I⁻] [HClO] =K [I⁻] [(k₁/k₂) [ClO⁻] [H₂O]/[OH⁻]] = (kk₁/k₂) [I⁻][ClO⁻] [H₂O]/[OH⁻]
Then from step 3
rate = k[OH-][HIO]
k₃ [OH-][HIO] = k₄ [H₂O] [IO⁻]
[H₂O]/[OH-] = (k₃/k₄) [HIO]/[[IO⁻]
Rate = (Kk₁/k₂) [I⁻][ClO⁻] [H₂O]/[OH⁻] =(kk₁/k₂) [I⁻][ClO⁻] [(k₃/k₄) [HIO]/[IO⁻]
Rate = (kk₁k₃/k₂k₄) [I⁻][ClO⁻][HIO]/[IO⁻]
(kk₁k₃/k₂k₄) = K
Rate = K [I⁻][ClO⁻][HIO]/[IO⁻]
Actual rate law: rate = k[ClO-][I -]
Rate Law obtained from this mechanism
Rate = K [I⁻][ClO⁻][HIO]/[IO⁻]
Hence, this mechanism isn't consistent with the actual rate law.
Hope this Helps!!!
