1
Question
The value of rate constant of a pseudo first order reaction ____________.
The value of rate constant of a pseudo first order reaction ____________.
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Solution
The correct option is D depends on the concentration of reactants present in excess.
A pseudo first-order reaction can be defined as a second order or bimolecular reaction that is made to behave like a first-order reaction, This reaction occurs when one reactant is present in excess or is mantained at a constant concentration compared with the other substance.
For example,a second-order reaction is given by the equation
A+B→C+D
This reaction is dependent upon the concentrations of both A and B but one of the components is present in large excess and thus its concentration hardly changes as the reaction proceeds.
So, if component B is in large excess and the concentration of B is very high as compared to that of A, the reaction is considered to be a pseudo-first-order reaction with respect to A and if component A is in large excess and the concentration of A is very high as compared to that of B, the reaction is considered to be pseudo-first order with respect to B.
For example, consider the Hydrolysis of ester:
CH3COOC2H3+H2O→CH3COOH+C2H3OH
Ethyl ethanoate Ethanoic acid Ethanol
Rate of reactionk=[CH3COOC2H3][H2O]
But if [H2O]>>>[CH3COOOC2H3]
Concentration of water will remain almost constant during the reaction.
Therefore,
Rate of reaction =k′[CH3COOC2H3]
Where,k′=k[H2O]
Therefore, hydrolysis of ester is pseudo first order reaction if H2O is taken in excess amount.
And thus, the value of rate constant is dependent on the concentration of reactants present in excess in a pseudo first order reaction.
Hence, option (B) is correct
depends on the concentration of reactants present in excess.
A pseudo first-order reaction can be defined as a second order or bimolecular reaction that is made to behave like a first-order reaction, This reaction occurs when one reactant is present in excess or is mantained at a constant concentration compared with the other substance.
For example,a second-order reaction is given by the equation
A+B→C+D
This reaction is dependent upon the concentrations of both A and B but one of the components is present in large excess and thus its concentration hardly changes as the reaction proceeds.
So, if component B is in large excess and the concentration of B is very high as compared to that of A, the reaction is considered to be a pseudo-first-order reaction with respect to A and if component A is in large excess and the concentration of A is very high as compared to that of B, the reaction is considered to be pseudo-first order with respect to B.
For example, consider the Hydrolysis of ester:
CH3COOC2H3+H2O→CH3COOH+C2H3OH
Ethyl ethanoate Ethanoic acid Ethanol
Rate of reactionk=[CH3COOC2H3][H2O]
But if [H2O]>>>[CH3COOOC2H3]
Concentration of water will remain almost constant during the reaction.
Therefore,
Rate of reaction =k′[CH3COOC2H3]
Where,k′=k[H2O]
Therefore, hydrolysis of ester is pseudo first order reaction if H2O is taken in excess amount.
And thus, the value of rate constant is dependent on the concentration of reactants present in excess in a pseudo first order reaction.
Hence, option (B) is correct
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