K1. Lasers are often used in kinetics experiments. Which energy level diagram do
ID: 694544 • Letter: K
Question
K1. Lasers are often used in kinetics experiments. Which energy level diagram does NOT represent a laser system? A) Excitation (D) K2. The reaction coordinate diagram for the conversion of 1-butene to cis- and trans-2-butene on a MgSO surface at 350 K is shown. E 1-butene cis-2-butene trans-2-butene Reaction Coordinate What is the relationship between the concentrations of the cis and trans isomers once equilibrium is reached? (A) [cis] [trans (B) [cis] [trans (C) [cis]> Irans (D) The final concentration depends on the total pressure of the gases K3. The vibrational frequency for gaseous carbon monoxide is 2170 cm. As CO chemisorbs on a metal surface, the vibrational frequency is expected to (A) remain unchanged. (B) increase because the C-O bond gets stronger when it attaches to a metal surface. (C) decrease because of the decreased electron density between the carbon atom and the oxygen atom. increase because of the increased electron density between the carbon atom and the metal surface. (D)Explanation / Answer
K2-B
Because we see from the energy profile that the activation energy for both the products are the same. So kinetics doesn't play a role. Whereas trans is more stable than cis as evident from the plot. This implies thermodynamics will govern the distribution of the products. Hence, trans> cis.
K3-C
Because electron density of C-O bond is shared with the metal and the bond weakens. The Lennard Jones potential under the harmonic oscillator approximation is like a parabola (i.e. the nond is like a spring with spring constant k. Sharper the parabola, higher is the value of k, stronger the bond). This means k decreases. Since frequency is proportional to k^(1/2), frequency(vibrational) decreases.
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