chapter 17 spectroscopy

Question 1

what do covalent bonds naturally due to possessing energy?

Answer 1

vibrate around a central point

Question 2

what does absorbing IR radiation do to covalent bonds?

Answer 2

makes them bend or stretch even more

Question 3

what are the two main types of vibration caused by IR radiation?

Answer 3

stretching and bending

Question 4

describe the stretch vibration.

Answer 4

a rhythmic movement along the line between the atoms so that the distance between the atomic centres increases and decreases

Question 5

describe the bend vibration.

Answer 5

it changes the bond angle of the covalent bond

Question 6

what effects the amount a bond stretches or bends?

Answer 6

•mass of atoms in bond, heavier atoms vibrate more slowly than lighter atoms
•strength of bond, stronger bonds vibrate faster than weaker bonds

Question 7

what type of radiation can a bond absorb?

Answer 7

radiation with the same frequency as the bonds natural frequency

Question 8

what is wavenumber?

Answer 8

a scale proportional to frequency with the units cm^-1

Question 9

describe the process of global warming.

Answer 9

•most of the suns visible and IR radiation passes through the atmosphere to the surface where most of it is absorbed
•however some is re emitted from the surface as long wavelength IR radiation
•greenhouse gases absorb this type of radiation as it has the same frequency as their natural frequency
•eventually these vibrating bonds re emitted this energy as radiation increasing the temperature of the atmosphere