Chemical Kinetics: JEE Main Chemistry Question with Solution
The number of correct statement/s from the following is
A. Larger the activation energy, smaller is the value of the rate constant.
B. The higher is the activation energy, higher is the value of the temperature coefficient.
C. At lower temperatures, increase in temperature causes more change in the value of k than at higher temperature
D. A plot of lnkvvT1 is a straight line with slope equal to −REa
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Hint 1 of 3
According to the Arrhenius equation k=Ae−Ea/(RT), how does the rate constant k depend on the activation energy Ea and what is the slope of lnk versus 1/T?
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Step-by-step solutionView
Correct answer
All four statements (A, B, C, and D) are correct, so the answer is 4.
Option analysis
Why each option works or fails
Reviewed route
Solution
StepWorking
01given
Four statements regarding the Arrhenius equation k=Ae−Ea/RT:
A. Larger activation energy implies smaller rate constant.
B. Higher activation energy implies higher temperature coefficient.
C. At lower temperatures, an increase in temperature causes a larger relative change in k than at higher temperatures.
D. A plot of lnk vs 1/T is a straight line with slope equal to −Ea/R.
02find
The total count of correct statements among A, B, C, and D.
03strategise
Use the Arrhenius relation k=Ae−Ea/(RT) and its logarithmic form lnk=lnA−RTEa to test each statement individually.
04execute
Statement A: Since k=Ae−Ea/RT, as Ea increases, the exponent −Ea/RT becomes more negative, hence k decreases. Thus, A is correct.
Statement B: The temperature coefficient is kTkT+10=exp[REa(T(T+10)10)]. As Ea increases, this ratio increases. Thus, B is correct.
Statement C: From dTdlnk=RT2Ea, the fractional change in k per degree, k1dTdk, is inversely proportional to T2. Hence, at lower T, temperature increase causes a greater change/sensitivity in k than at higher T. Thus, C is correct.
Statement D: Plotting lnk vs T1 gives lnk=lnA−(REa)T1, which is a straight line y=c+mx with slope m=−REa. Thus, D is correct.
Total correct statements = 1 + 1 + 1 + 1 = 4.
✓verify
All four statements are well-established theoretical properties of the Arrhenius rate law in Chemical Kinetics. Total count is 4.
Hints that build this answer step by step
According to the Arrhenius equation k=Ae−Ea/(RT), how does the rate constant k depend on the activation energy Ea and what is the slope of lnk versus 1/T?
Larger Ea yields a smaller k, and the slope of lnk vs 1/T is −Ea/R.
From the differential Arrhenius form dTd(lnk)=RT2Ea, how do the temperature coefficient (fractional change in k with temperature) and temperature level influence the sensitivity of k?
Higher Ea gives a higher temperature coefficient, and the sensitivity is greater at lower temperatures (due to 1/T2).
How many of the statements A, B, C, and D are correct?
Why does a temperature increase cause a greater effect at lower temperatures in statement C?
Because the derivative dTdlnk=RT2Ea has T2 in the denominator. When T is small, T21 is much larger, meaning the rate constant is much more sensitive to changes in temperature at low temperatures.