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For the reaction:
[Cr(H2O)6]3+ + [SCN] → [Cr(H2O)5NCS]2+ + H2O
The rate law is: r = k[Cr(H2O)6]3+ + [SCN].
The value of k is 2.0 × 10–6 L mol–1 s–1 at 14 °C and 2.2 × 10–5 L mol–1 s–1 at 30 °C. What is the value of Ea?
  • a)
    26 kcal mol–1
  • b)
    2.6 kcal mol–1
  • c)
    2600 kcal mol–1
  • d)
    260 kcal mol–1
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
For the reaction:[Cr(H2O)6]3+ + [SCN–] → [Cr(H2O)5NCS]2+ + H2OThe rat...
Use Arrhenius equation
T1 = 273 + 14 = 287 K,
T2 = 273 + 30 = 303 K
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Most Upvoted Answer
For the reaction:[Cr(H2O)6]3+ + [SCN–] → [Cr(H2O)5NCS]2+ + H2OThe rat...
Calculation of Activation Energy (Ea)

Given Data:
- k1 = 2.0 × 10^–6 L mol^–1 s^–1 (at 14 °C)
- k2 = 2.2 × 10^–5 L mol^–1 s^–1 (at 30 °C)

Arrhenius Equation:
The rate constant k is related to the temperature (T) and the activation energy (Ea) by the Arrhenius equation:
k = A * e^(-Ea/RT)

Calculating Ea:
1. Take the ratio of rate constants k1 and k2:
k2/k1 = (A * e^(-Ea/RT2)) / (A * e^(-Ea/RT1))
2. Simplify the equation:
e^(-Ea/R * (1/T2 - 1/T1)) = k2/k1
3. Substitute the given values and solve for Ea:
e^(-Ea/R * (1/303 - 1/287)) = 2.2 × 10^–5 / 2.0 × 10^–6
e^(-Ea/8.314 * (0.0033)) = 11
e^(-Ea/0.0274) = 11
-Ea/0.0274 = ln(11)
Ea = -0.0274 * ln(11)
Ea ≈ 26 kcal mol^–1
Therefore, the value of Activation Energy (Ea) is approximately 26 kcal mol^–1. Hence, the correct answer is option 'A'.
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Question Description
For the reaction:[Cr(H2O)6]3+ + [SCN–] → [Cr(H2O)5NCS]2+ + H2OThe rate law is: r = k[Cr(H2O)6]3+ + [SCN–].The value of k is 2.0 × 10–6 L mol–1 s–1 at 14 °C and 2.2 × 10–5 L mol–1 s–1 at 30 °C. What is the value of Ea?a)26 kcal mol–1b)2.6 kcal mol–1c)2600 kcal mol–1d)260 kcal mol–1Correct answer is option 'A'. Can you explain this answer? for NEET 2025 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about For the reaction:[Cr(H2O)6]3+ + [SCN–] → [Cr(H2O)5NCS]2+ + H2OThe rate law is: r = k[Cr(H2O)6]3+ + [SCN–].The value of k is 2.0 × 10–6 L mol–1 s–1 at 14 °C and 2.2 × 10–5 L mol–1 s–1 at 30 °C. What is the value of Ea?a)26 kcal mol–1b)2.6 kcal mol–1c)2600 kcal mol–1d)260 kcal mol–1Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for NEET 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for For the reaction:[Cr(H2O)6]3+ + [SCN–] → [Cr(H2O)5NCS]2+ + H2OThe rate law is: r = k[Cr(H2O)6]3+ + [SCN–].The value of k is 2.0 × 10–6 L mol–1 s–1 at 14 °C and 2.2 × 10–5 L mol–1 s–1 at 30 °C. What is the value of Ea?a)26 kcal mol–1b)2.6 kcal mol–1c)2600 kcal mol–1d)260 kcal mol–1Correct answer is option 'A'. Can you explain this answer?.
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