Tag: electrochemistry and chemical kinetics

Questions Related to electrochemistry and chemical kinetics

In pseudo unimolecule reactions:

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. both the reactants are present in low concentration

  2. Both the reactants are present in same concentration

  3. One of the reactant is present in excess

  4. One of the reactant is non-reactive

Show answer
Correct Option: C
Explanation:

Pseudo Unimolecular Reaction. The reactions having molecularity two but the order of reaction is one is called pseudo unimolecular reactions,in such type of reactions, one reagent is take in the excess amount so that the disappearance of that reagent is negligible and it does not determine the rate of reaction.

Example:
  • Hydrolysis of ester$CH _3COOC _2H _5$,
  • Hydrolysis of sucrose.

The value of rate of a pseudo first order reaction depends upon:

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. the concentration of both the reactants present in the reaction

  2. the concentration of the reactant present in small amount

  3. the concentration of the reactant present in excess

  4. the value of $\Delta H$ of the reaction

Show answer
Correct Option: B
Explanation:

$CH _3COOC _2H _5 + H _2O \rightarrow CH _3COOH + CH _3OH$
          0.01                    10                   0                      0

            0                      9.99              0.01               0.01 

The above reaction is a Pseudo first order reaction. As it can be seen from the above reaction that the concentration of water is not changing much. Thus the rate of the reaction is not much affacted by the change in concentration of  water. However rate of the reaction get significantly affacted by the concentration gradient of ethyl acetate. Hence, the rate of Pseudo first order reaction depends upon the concentration of the reactant present in small amount.

Option B is correct.

         

The value of rate constant of a pseudo first order reaction ________.

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. depends on the concentration of reactants present in small amount

  2. depends on the concentration of reactants present in excess

  3. is independent of the concentration of reactants

  4. depends only on temperature

Show answer
Correct Option: B
Explanation:

Pseudo first-order reaction is not the first-order reaction by nature. It is made the first order by adding something in excess.so, the rate constant depends on the concentration of reactants present in excess.

Which of the following is/are correct?

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. Acid hydrolysis of an ester follows pseudo first order kinetics

  2. Inversion of cane sugar follows pseudo first order kinetics

  3. Decomposition of varous gases on the surface of metallic catalysts, such as decomposition of $HI$ on gold surface also exhibits zero roder kinetics

  4. Radioactivity follows first order kinetics

Show answer
Correct Option: A,B,C,D
Explanation:

 Pseudo first order reaction is a reaction in which concentration of one of the species dominates over the other. Hence the reaction follows the first order kinetics.

Options A, B and C all are the examples of pseudo first order reaction.
Radioactive decay follows first order reaction.

$\mathbf {Hence\ all\ the\ options\ are\ correct.}$

Nitrosy ligand binds to d-metal atoms in liner and bent fashion and behaves, respectively, as _______________.

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. $NO^{+}$ and $NO^{+}$

  2. $NO^{+}$ and $NO^{-}$

  3. $NO^{-}$ and $NO^{-}$

  4. $NO^{-}$ and $NO^{+}$

Show answer
Correct Option: B

Triple point temperature for water is nearly:

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. $273.16K$

  2. $373.16K$

  3. ${100}^{o}C$

  4. ${444.6}^{o}C$

Show answer
Correct Option: A
Explanation:

Triple point temperature for water is nearly $0.01^{o} \ C$, which is $273.16 \ K$.

Hence, option A is correct.

Which of the following is pseudo-unimolecular reaction?

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. $2{ H } _{ 2 }{ O } _{ 2 }\longrightarrow 2{ H } _{ 2 }O+{ O } _{ 2 }$

  2. ${ C } _{ 6 }{ H } _{ 5 }{ N } _{ 2 }Cl+HOH\longrightarrow { C } _{ 6 }{ H } _{ 5 }OH+{ N } _{ 2 }+HCl$

  3. $C{ H } _{ 3 }COO{ C } _{ 2 }{ H } _{ 5 }+NaOH\longrightarrow C{ H } _{ 3 }COONa+{ C } _{ 2 }{ H } _{ 5 }OH$

  4. $2{ O } _{ 3 }\longrightarrow 3{ O } _{ 2 }$

Show answer
Correct Option: B
Explanation:

In a chemical reaction if two or more reactants are involved but the rate of reaction depends only upon the concentration of one of the reactant and independent of other reactants then it is said to be a pseudo unimolecular reaction.

so the option B shows the pseudotype of reaction 

Rate law for the following reaction; $Ester+H^+\rightleftharpoons Acids+ Alcohol$; is $\frac {dx}{dt}=k [ester]^1 [H^+]^0$. What would be the effect on the rate if concentration of $H^+$ ion is doubled?

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. Same

  2. Doubled

  3. Half

  4. Data insufficient

Show answer
Correct Option: A
Explanation:

As reaction does not depend on the concentration of $H^+$, therefore, rate will be the same.

A first-order reaction which is $30\%$ complete in $30$ minutes has a half-life period of:

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. $24.2\ min$

  2. $58.2\ min$

  3. $102.2\ min$

  4. $120.2\ min$

Show answer
Correct Option: B
Explanation:

It is a 1st order reaction


$k = \dfrac{2.303}{t} log \dfrac{a}{a-x}$

but $k=\dfrac{0.693}{t _{\frac{1}{2}}}$

$\dfrac{0.693}{{t} _{1/2}} = \dfrac{2.303}{30} log \dfrac{100}{70}$

${t} _{1/2} = 58.2 min$

Hence, the correct option is $B$

The acid hydrolysis of an ester is___________.

pseudo first order reaction order of reactions chemical kinetics electrochemistry and chemical kinetics chemistry

  1. Pseudo first order reaction

  2. Bimolecular reaction

  3. Pseudo unimolecular reactions

  4. None of the above

Show answer
Correct Option: A,C