Question

1.)

a.)How many kinetic energy modes does a triatomic molecule have?

b.)Treating the molecule as one particle, how many translational kinetic energy terms does it have? what about rotational kinetic energy terms?

c.)How many vibrational kinetic energy modes can this molecule have, if the total number of kinetic energy modes is what you found in a.

d.)Count all vibrational modes. Categorize the modes into types of kinetic and potential energy modes

e.)Find the total number of modes for a gas of Na Triatomic molecules

Answer 1

a) A linear triatomic molecule (eg CO₂) has total kinetic energy modes = 5

A non-linear triatomic molecule (eg. O₃) has total kinetic energy modes = 6

b) A linear triatomic molecule has three translational and two rotational energy terms.

A non-linear triatomic molecule has three translation and three rotational energy terms.

c) For a linear molecule, vibration modes = 6N - 10 = 6(3) - 10 = 8

For a non-linear molecule, vibration modes = 6N-12 = 6(3) = 12 = 6

d) Vibrational modes in a tri-atomic molecule are:

i. Symmetric stretching

ii. Asymmetric stretching

iii. Scissoring (bending)