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3. Chemical kinetics — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistry3. Chemical kinetics1 Mark
MCQ
For a first order reaction
  • A
    The degree of dissociation is equal to $(1 - {e^{ - kt}})$
  • B
    A plot of reciprocal concentration of the reactant vs time gives a straight line
  • C
    The pre-exponential factor in the Arrhenius equation has the dimension of time ${T^{ - 1}}$
  • ✓
    Both $(a)$ and $(c)$
✓

Answer

Correct option: D.
Both $(a)$ and $(c)$
d
$(a)$ is correct because degree of dissociation $ = 1 - {e^{ - kt}}$ at any time $t.$

$(b)$ is wrong because plot of $\log$ $ [A] $ vs $  t$ is a straight line

$(c)$ is wrong because time taken for $75\%$ reaction is two half life.

$(d)$ is correct because in $k = A{e^{ - {E_a}/RT}}$, ${E_{a/RT}}$ is dimensionless hence $A$ has the unit of $K.$

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