Question

1.

a. Using Beer-Lambert equation (A=eCL) to explain how absorbance is affected by changes in concentration and in the pathlength.

b. How to use the molecular structure to predict which molecules will absorb radiation in the IR region

c. Explain the mechanism by which greenhouse gases result in higher atmospheric temperature.

d. Explain why the wavelength at which a molecule absorbs energy is important in determining whether a molecule will act as a greenhouse gas.

e. Explain the importance of the solar window and the atmospheric window (also called thermal window)

Answer 1

NOTE: Dear candidate you have askd too many question. Still here we answer first four parts

(a) Beer-Lamberts law states that

A=ecl

A = absorbance, e = absorbtivity, c = concentration, path Length of solution

As is evident the absorbtion is directly related to concentration and pathlength of the solution. Hence an increase in the concentrtion or the pathlength will increase the absorbtion, and decrease in concentration or pathlength will decrese the Absorbtion.

(b) All the molecules exhibit different typs motions like rotaation , vibration, translation etc. Absorbtion of IR radiation is relted with the vibrational motion of a molecule. If the dipole moment of a molecule chnges by its vibration the molecule will absorb IR radiation. Homonuclear molecules like H₂, N₂ etc does not involve change in dipole moment on vibration.Some of the vibrations of carbondioxide CO₂ (O=C=O) are accompanied by change in dipole moment hence it will absorb IR radiation.

(C) Green house gases have a property of absorbing IR radiations (Also called heat radiations) Upon absorbtion of radiation the gases become warm and increase the temperature of atmosphere.

(d) Differen molecules absorb different wavelengths. Some of these wavelengths e.g; wavelength of IR radiation is responsible for heating up of atmosphere. Hence the molecules which aabsorb IR radiation het up te atmosphere. This makes the wavelength important at which a molecule absorb.