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Can someone help me with this, - Chemical kinetics - JEE Main

Consider the reaction :

The rate of reaction for this reaction is

Rate =K\left [ Cl_{2} \right ]\left [ H_{2}S \right ]

Which of these mechanism is/are consistent with this rate equation ?

A\: \: \: \: Cl_{2}+H_{2}S\rightarrow H^{+}+Cl^{-}+Cl^{+}+HS^{-}\left ( slow \right )

        \: \: \: \: Cl^{+}+HS^{-}\rightarrow H^{+}+Cl^{-}+S\left ( fast \right )

B\: \: \: \: H_{2}S\Leftrightarrow H^{+}+HS^{-}\left ( fast\: equilibrium \right )

        Cl_{2}+HS^{-}\rightarrow 2Cl^{-}+H^{+}+S\left ( Slow \right )

 

 

  • Option 1)

    A only

  • Option 2)

    B only

  • Option 3)

    Both A and B

  • Option 4)

    Neither A nor B

 
Answers (1)
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As we learnt in 

Rate Determining Step -

The overall rate of reaction is controlled by the slowest step in a reaction called the rate determining step.

- wherein

e.g.

2H_{2}O_{2}\xrightarrow[alkaline\ medium]{I^{-}}2H_{2}O+O_{2}

r=\frac{-d[H_{2}O_{2}]}{dt}=K[H_{2}O_{2}][I^{-}]

H_{2}O_{2}+I^{-}\underset{slow}{\rightarrow}H_{2}O+IO

H_{2}O_{2}+IO^{-}\underset{fast}{\rightarrow}H_{2}O+I+O_{2}^{-}

 

For Reaction     Cl_{2} + H_{2} S \rightarrow S + 2H^{+} + 2Cl^{-}\\

 

The Mechanism is (a)\;Cl_{2} + H_{2}S \rightarrow H^{+}+Cl^{-}+Cl^{+}+HS^{-}\: (Slow)

(b)\;Cl^{+} + HS^{-}\rightarrow H^{+}+ Cl^{-}+S\; (fast)

 


Option 1)

A only

This option is correct. 

Option 2)

B only

This option is incorrect. 

Option 3)

Both A and B

This option is incorrect. 

Option 4)

Neither A nor B

This option is incorrect. 

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