A molecule can absorb a 552 nm photon. However, a photon that it emits has longe

Question

A molecule can absorb a 552 nm photon. However, a photon that it emits has longer, 660 nm wavelength.

1. What is the change of energy of this molecule after the absorption of a 552 nm photon, followed by the emission of a 60 nm photon?

2. What is the total energy change (absorbed as heat) after one mole of molecules absorbs and then emits a photon with the frequencies specified above?

3. What is the molar heat capacity of this compound if upon absorption of heat calculated in part (b) the temperature of the compound increases by 3.5 C?

Explanation / Answer

A molecule can absorb a 552 nm photon. However, a photon that it emits has longer, 660 nm wavelength.

1. What is the change of energy of this molecule after the absorption of a 552 nm photon, followed by the emission of a 660 nm photon?

Change in wavelength = 660 nm-552 nm

= 108 nm

E = h

And = c/

Then;

E = h c/

c = speed of light (3.00 x 10^8 m/s)
E = energy
h = Planck's constant (6.63 x 10^-34 J-s)
= wavelength , 108 nm or 108*10^-9 m
= frequency

E= 6.63 x 10^-34 J-s * 3.00*10^8 m/s/ 108*10^-9 m

= 1.84 *10^-18 J

2. What is the total energy change (absorbed as heat) after one mole of molecules absorbs and then emits a photon with the frequencies specified above?

1 mol = 6.23 *10^23 photon

The total energy change (absorbed as heat) after one mole of molecules absorbs and then emits a photon with the frequencies specified above =

6.23 *10^23 photon/ mol * 1.84 *10^-18 J/ photon

=11.46*10^5 J/mol

3. What is the molar heat capacity of this compound if upon absorption of heat calculated in part (b) the temperature of the compound increases by 3.5 C?

Total energy = molar heat capacity* temp change

11.46*10^5 J / mol= molar heat capacity* 3.5 C

Molar heat capacity= 3.27 J / mol-C

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