Question

It takes 945. kJ/mol to break a nitrogen-nitrogen triple bond. Calculate the maximum wavelength of light for which a nitrogen-nitrogen triple bond could be broken by absorbing a single photon. Be sure your answer has the correct number of significant digits.

Answer 1

Answer: 1.274 * 10^ -7 meter (same as 127.4 nanometers

Explanation:

It's given that the energy

required to break the N N triple bond is 945 * 10^3 joules per mole.

One mole contains 6.02 * 10^ 23 molecules, so the energy required per molecule

= 945 * 10^3 / 6.023 * 10^23, or 1.56 * 10^-18 joules.

Then we need a photon whose energy (E) is at least that amount.

The energy E of a photon is related to its frequency f by PLANCK'S EQUATUON,

E = hf,

where h is Planck's constant (6.625 * 10^-34 joule-sec)

and the wavelength w is inversely proportional to the frequency by w = c/f, where c is the speed of light, 2.998 * 10^8 meters per sec.

If h & c are both constants, their product hc is constant, so we can say E = hc/w,

or if we know E and want to find w, a little algebra gives: w = hc/E.

The product hc = 1.9875 * 10^-25 joule-meters,

so w = 1.9875 * 10^-25 / 1.56 * 10^-18, or 1.274 * 10^ -7 meter (same as 127.4 nanometers