Question

Nitric oxide emitted from the engines of supersonic aircraft can contribute to the destruction of stratospheric ozone: This reaction is highly exothermic (ΔE=−201kJ), and its equilibrium constant Kc is 3.4×1034 at 300 K.

Part A Which rate constant is larger, kf or kr? kf kr

Part B The value of kf at 300 K is 8.2×106 M−1s−1 . What is the value of kr at the same temperature? Express your answer to two significant figures and include the appropriate units. 2.4•10−28 M−1S−1 SubmitMy AnswersGive Up Incorrect; Try Again; 7 attempts remaining

Part C

A typical temperature in the stratosphere is 230 K. Do the values of kf, kr, and Kc increase or decrease when the temperature is lowered from 300 K to 230 K? A typical temperature in the stratosphere is 230 .

kf and kr increase, Kc decreases

kf and Kc decrease, kr increases Kc and kr decrease, kf increases

kf and kr decrease, Kc increases

All of this values decrease.

All of this values increase.

Answer 1

Part-A: For a chemical reaction in equilibrium, Kc = Kf / Kr

Given Kc = Kf / Kr = 3.4*10³⁴ (at 300 K)

So Kc > 1

=> Kf / Kr > 1

=> Kf > Kr

Hence Kf is larger

Part-B: Given Kf = 8.2×10⁶ M^-1s^-1

Kc = 3.4*10³⁴ = Kf / Kr

=> 3.4*10³⁴ = 8.2×10⁶ M^-1s^-1 / Kr

=> Kr = 8.2×10⁶ M^-1s^-1 / 3.4*10³⁴

=> Kr = 2.4*10^-28 M^-1s^-1(Answer)

Part-C: Kc (= Kf/Kr) decreases with decrease in temperature

Since Kc is directly proportional to Kf, Kf will also decrease.

Since Kc is inversely proportional to Kr, Kr will increase

Hence kf and Kc decrease, kr increases