The half-life of a substance in a certain enzyme catalysed reaction is 138 s. The time required for the concentration of the substance to fall from $$1.28 mg L^{-1}$$ to $$0.04 mg L^{-1}$$ is:
Given:-
$$t{ 1 }/{ 2 }$$ of enzyme catalyzed reaction$$=138s$$
Initial concentration of substance$$=1.28{ ㎎ }/{ ℓ }$$
Final concentration of substance$$=0.04{ ㎎ }/{ ℓ }$$
Enzyme catalyzed reactions follow first order kinetics
Fall of concentration from $$1.28{ ㎎ }/{ ℓ }$$ to $$0.04{ ㎎ }/{ ℓ }$$ involves $$5$$ half lives
$$1.28\quad \underrightarrow { t{ 1 }/{ 2 } } \quad 0.64\quad \underrightarrow { t{ 1 }/{ 2 } } \quad 0.32\quad \underrightarrow { t{ 1 }/{ 2 } }\quad 0.16\quad \underrightarrow { t{ 1 }/{ 2 } } \quad 0.08\quad \underrightarrow { t{ 1 }/{ 2 } }\quad 0.04$$
$$\therefore $$Time required$$=5\times t{ 1 }/{ 2 }$$
$$=\left( 5\times 138 \right) s$$
$$=690s$$
Note:- Half life of a reaction is the time required for the reactant concentration to decrease to one-half its initial values.
Here, the fall of concentration from $$1.28$$ to $$0.04{ ㎎ }/{ ℓ }$$ required $$5$$ half-lives; and each half-life required $$138$$ seconds.
Hence; the correct answer is $$690$$ seconds, which is the total time required for the concentration of the substance to fall from $$1.28{ ㎎ }/{ ℓ }$$ to $$0.04{ ㎎ }/{ ℓ }$$
Consider the following reactions at 300 K: X $$\rightarrow$$ Y (uncatalysed reaction) & X $$\rightarrow$$ Y (catalysed reaction). The energy of activation is lowered by 83.14 kJmol$$^{-1}$$ for the catalysed reaction. The rate of catalysed reaction is:
For a given reaction, energy of activation for forward reaction $$(E_{af})$$ is $$80kJ.mol^{-1}.$$ $$\Delta H = -40kJ.mol^{-1}$$ for the reaction. A catalyst lowers $$E_{af}$$ to $$20 kJ.mol^{-1}.$$ The ratio of energy of activation for reverse reaction before and after addition of catalyst is :
The role of a catalyst is to change _______.
Which of the following statements about the catalyst is true?
Which of the following factors are responsible for the increase in the rate of a surface catalyzed reaction? (i) A catalyst provides proper orientation for the reactant molecules to react. (ii) The heat of adsorption of reactants on a catalyst helps reactant molecules to overcome activation energy. (iii) The catalyst increases the activation energy of the reaction.
What is the role of desorption in the process of catalysts?
How does a catalyst work?
Give reasons for the following: Rough surface of catalyst is more effective than smooth surface.
Identify the true statement(s):
A catalyst is a substance which