CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 16 - MCQExams.com

The half-life of $$_6 C^{14}$$, if its decay constant is $$6.31 \times 10^{-4}$$ is:
  • 1098 yrs
  • 109.8 yrs
  • 10.98 yrs
  • 1.098 yrs
$$\dfrac{15}{16} \ th$$ of a radioactive sample decays in 40 days half-life of the sample is:
  • 100 days
  • 10 days
  • 1 day
  • $$log_e$$ 2 days
A first-order nuclear reaction is half completed in 45 minutes. How long does it need $$99.9 \%$$ of the reaction to be completed?
  • 5 hours
  • 7.5 hours
  • 10 hours
  • 20 hours
Assertion : Order of the reaction can be zero or fractional.
Reason    : We cannot determine order from the balanced chemical equation.
  • Both assertion and reason are correct and the reason is correct explanation of assertion.
  • Both assertion and reason are correct but reason does not explain assertion.
  • Assertion is correct but reason is incorrect.
  • Both assertion and reason are incorrect.
  • Assertion is incorrect but reason is correct.
Which of the following statement is incorrect ?
  • Unit of rate of disappearance is $$Ms^{-1}$$
  • Unit of rate of reaction is $$Ms^{-1}$$
  • Unit of rate constant k depends upon order
  • Unit of k for first order reaction is $$Ms^{-1}$$
the rate constant for a first order reaction is $$ 2 \times 10^{-2} min^{-1} $$ the half -life period of reaction is 
  • $$ 69.3 min $$
  • $$ 34.65 min $$
  • $$ 17.37 min $$
  • $$ 3.46 min $$
The activation energy in a chemical reaction is defined as 

  • the difference in energies of reactants and products
  • the sum of energy of reactant and products
  • the difference in energy of intermediate complex with the average of reactants and products
  • the difference in energy of intermediate complex and the average energy of reactants.
Cyclopropane rearranges to form propene
$$ \Delta \rightarrow CH_3 -CH =CH_2 $$
this follows first order kinetics. the rate constant is $$ 2.714 \times 10^{-3} sec^{-1} $$the initial concentration of cyclopropane is $$ 0.29 M $$what will be concentration  of cyclopropane after 100 sec ?
  • $$ 0.035 M $$
  • $$ 0.22 M $$
  • $$ 0.145 M $$
  • $$ 0.0018 M $$
Fill up the following with suitable terms.

$$(i)$$ Activation energy = Threshold energy - _____________
$$(ii)$$ Half-life period of zero order reaction =_____________
$$(iii)$$ Average rate of reaction = _____________
$$(iv)$$ Instantaneous rate of reaction =____________

  • Potential energy ,   $$\dfrac { 0.693}{k}\ ,\ \quad \dfrac {dx}{dt}\ ,\ \quad \dfrac { \Delta [A] }{\Delta t } $$
  • Energy of reactants ,  $$ \dfrac {1}{k}\ ,\  \quad \dfrac { \Delta [A] }{ \Delta t }\ ,\ \quad \dfrac {dx}{dt} $$
  • Energy of reaction  ,  $$ \dfrac { log k}{t}\ ,\  \quad \dfrac { \Delta [A] }{\Delta t }\ ,\  \quad \dfrac {dx}{dt} $$
  • Average kinetic energy of reactants ,  $$ \dfrac {a}{2k} \ ,\ \quad \dfrac { \Delta [A] }{ \Delta t }\ ,\  \quad \dfrac {dx}{dt} $$
Which of the following is incorrect statement ?
  • Stoichiometry of a reaction tells about the order of the elementary reactions
  • For a zero order reaction, rate and the rate constant are idneitcal.
  • A zero order reaction is controlled by factors other than concentration of reactants
  • A zero order reaction is an elementary reaction
The activation energy of the reaction, $$A + B \rightarrow C + D + 38kcal$$ is $$20$$ kcal, What would be the activation energy of the reaction,
$$C + D \rightarrow A + B$$
  • $$20\,kcal$$
  • $$-20 \,kcal$$
  • $$18\,kcal$$
  • $$58\,kcal$$
One or more answers is/are correct.
Select the correct statement(s):
  • Every substance that appears in the rate law of reaction must be a reactant or product in that reaction
  • If we know that rate law of a reaction; we can deduce it's mechanism must be elementary
  • If the reaction has rate $$r = k[A][B]^{3/2}$$ then reaction may be elementary
  • A zero order reaction must be a complex reaction
An increase in the concentration of the reactants of reaction leads to change in :
  • Heat of reaction
  • Threshold energy
  • Collision frequency
  • Activation energy
When the activation energies of the forward and backward reactions are equal, then:
  • $$\Delta E = 0, \Delta S = 0$$
  • $$\Delta E = 0, \Delta G = 0$$
  • $$\Delta S = 0, \Delta G = 0$$
  • only $$\Delta E = 0$$
0:0:1


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