The gas-phase conversion reaction between the geometric isomers cis-2-butene and trans-2-butene is represented by the equation above. The value of the equilibrium constant, Key, for the reaction is 3.2 at 298 K and 1.0 atm. (a) In a mixture of the isomers at equilibrium at 298 K and 1.0 atm, which is present at a higher concentration, cis-2-butene or trans-2-butene? Justify your answer (b) If 1.00 mol of pure cis-2-butene and 1.0 mol of pure trans-2-butene were introduced into an evacuated container at 298 K, in which direction (to the right or to the left) would the reaction proced to establish (c) Given that Keg for the reaction at 400 K has the value 1.3, predict whether the reaction is endothermic or (d) There are other structural isomers of cis-2-butene and trans-2-butene. Draw one of these isomers, including equilibrium?

Question

Chemistry

Carina Keith

19 January, 21:45

The gas-phase conversion reaction between the geometric isomers cis-2-butene and trans-2-butene is represented by the equation above. The value of the equilibrium constant, Key, for the reaction is 3.2 at 298 K and 1.0 atm. (a) In a mixture of the isomers at equilibrium at 298 K and 1.0 atm, which is present at a higher concentration, cis-2-butene or trans-2-butene? Justify your answer (b) If 1.00 mol of pure cis-2-butene and 1.0 mol of pure trans-2-butene were introduced into an evacuated container at 298 K, in which direction (to the right or to the left) would the reaction proced to establish (c) Given that Keg for the reaction at 400 K has the value 1.3, predict whether the reaction is endothermic or (d) There are other structural isomers of cis-2-butene and trans-2-butene. Draw one of these isomers, including equilibrium?

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Answers (1)

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Nasir Odom · Answer 1

Part A: Trans-but-2-ene is present in higher concentration

Part B: The reaction will shift or proceed to the right

Part C: The reaction is exothermic

Part D: The other isomers are 1-butene, 2-methyi propene, cyclopropane and methylcyclopropane

Explanation:

An equilibrium reaction of cis-2-butene and trans-2-butene is shown below

cis-2-butene ⇔ trans-2-butene

Equilibrium constant (Kc) = concentration of product / concentration of reactant

Equilibrium constant (Kc) = 3.2

Part A: For the Kc to be greater than 1, therefore, The concentration of the numerator (concentration of product) should be higher compared to the concentration of reactant. Concentration of trans-2-butene is greater than cis-2-butene.

Part B: If 1.00 mol of pure cis-2-butene and 1.0 mol of pure trans-2-butene were present at equilibrium, then

Equilibrium constant (Kc) = 1 / 1

(Kc) = 1

This suggests that the reaction will shift to the left.

Part C: When the temperature was increased from 298K to 400K, there was a corresponding decrease on the equilibrium constant from 3.2 to 1.3. A smaller Kc is a result of smaller product (trans-2-butene). Therefore, the reaction has shifted to the left. The reaction has to be an exothermic reaction.

Part D:

The other isomers of But-2-ene are 1-butene, 2-methyi propene, cyclopropane and methylcyclopropane.

CH3 C (CH3) = CH2 (2-methyi propene,)

Equilibrium reaction: CH3CH=CHCH3 ⇔ CH3 C (CH3) = CH2

But-2-ene 2-methyl propene