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# Consider the reaction:Cl2(aq)+H2S(aq)→S(s)+2H+(aq)+2Cl−(aq)The rate equation for this reaction is rate =k[Cl2][H2S]Which of these mechanisms is /are consistant with this rate equation?(A) Cl2+H2S→H++Cl−+Cl++HS− (slow)Cl++HS−→H++Cl−+S (fast)(B) H2S⇌H++HS− (fast equilibrium)Cl2+HS−→2Cl−+H++S (slow)B onlyA onlyBoth A and BNeither A nor B

A
B only
B
Neither A nor B
C
Both A and B
D
A only
Solution
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#### Consider the reaction:Cl2(aq)+H2S(aq)→S(s)+2H+(aq)+2Cl−(aq)The rate equation for this reaction is rate =k[Cl2][H2S].The rate equation indicates that the reaction is first order in chlorine and first order in hydrogen sulphide.The mechanism (A) is consistent with this rate equation.(A) Cl2+H2S→H++Cl−+Cl++HS− (slow) Cl++HS−→H++Cl−+S (fast)The mechanism (A) is not consistent with this rate equation.(B) H2S⇌H++HS− (fast equilibrium) Cl2+HS−→2Cl−+H++S (slow)Based on mechanism (B), the rate equation will be rate =k[Cl2][H2S]1/2 and not rate =k[Cl2][H2S].From slow step , rate =k′[Cl2][HS−]......(1)From fast equilibrium step,K=[H+][HS−][H2S]=[HS−]2[H2S] (∵[H+]≃[HS−])[HS−]=(K[H2S])1/2......(2)Substitute (2) in (1) rate =k′[Cl2][HS−] rate =k′[Cl2](K[H2S])1/2 rate =k[Cl2][H2S]1/2

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Similar Questions
Q1
Consider the reaction:
Cl2(aq)+H2S(aq)S(s)+2H+(aq)+2Cl(aq)
The rate equation for this reaction is rate =k[Cl2][H2S]
Which of these mechanisms is /are consistant with this rate equation?
(A) Cl2+H2SH++Cl+Cl++HS (slow)
Cl++HSH++Cl+S (fast)
(B) H2SH++HS (fast equilibrium)
Cl2+HS2Cl+H++S (slow)
View Solution
Q2
Consider the reaction:
Cl2(aq.)+H2S(aq.)S(s)+2H+(aq.)+2Cl(aq.)
The rate equation for this reaction is:
Rate =k[Cl2][H2S]
Which of these mechanisms is/are consistent with this rate equation?
A. Cl2+H2SH++Cl+Cl++HS (slow)
Cl++HSH++Cl+S (fast)
B. H2SH++HS (fast equilibrium)
Cl2+HS2Cl+H++S (slow)
View Solution
Q3
Consider two alternative mechanism for the chlorination of methane. Which step is crucial in deciding which mechanism is not likely to be observed?
Mechanism I Mechanism II
 A Cl2⟶2Cl∙ A Cl2⟶2Cl∙ B Cl∙+CH4⟶HCl+∙CH3 D Cl∙+CH4⟶CH3Cl+H∙ C ∙CH3+Cl2⟶CH3Cl+Cl∙ E H∙+Cl2⟶HCl+Cl∙

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Q4
Ka1,Ka2 and Ka3 are the respective ionisation constants for the following reactions;
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View Solution
Q5
For the formation of phosgene from CO(g) and chlorine, CO(g)+Cl2(g)COCl2(g), the experimentally determined rate equation is, d[COCl2]dt=k[CO][Cl2]3/2.
Is the following mechanism consistent with the rate equation?
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