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(b) Which peak, the one at 365 nm or the one at 435 nm, results from the absorption of

photons with the greater energy? Justify your answer.
(c) Based on the diagram above, is the forward reaction endothermic or exothermic? Justify
your answer in terms of Le Châtelier's principle.

(b) Which peak, the one at 365 nm or the one at 435 nm, results from the absorption-example-1

1 Answer

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Answer:

365nm and Exothermic reaction

Step-by-step explanation:

b) The Einstein Planck's equation states that

E = hf where E is the energy of a photon

h is the Planck's constant

f is the frequency

But Frequency f = c/λ where c is the speed of light

λ is the wavelength

Therefore Energy E = hc/λ

From the above equation we see that the Energy of a photon is indirectly proportional to its wavelength

Hence as the wavelength increases from 365nm to 435nm, the energy of the photons decreases

Therefore, a photon will wavelength 365nm would have a higher energy than one will wavelength of 435nm.

c) From the diagram we observe the following:

At high temperatures, HPR⁺ occurs at a higher concentration than at low temperatures.

At low temperatures, more of PR⁻ is formed than at high temperatures

The equation of the reaction is

HPR⁺ (aq) ⁺ ⇆ H⁺ + PR⁻(aq)

Le Chartelier's principle states that when an external constraint such as a change in concentration, pressure or temperature is placed on a system in equilibrium, the system acts in such a way as to oppose the change.

Hence a decrease in temperature on the side of reactant, HPR would force the equilibrium to the side of the products, PR in other to accommodate the change

The forward reaction, which produces more of the product PR⁻ is exothermic because the at low temperatures, the the forward reaction is favoured and equilibrium shifts to the right.

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