General Chemistry Answers

You are given an aqueous solution containing similar concentrations of both calcium ions (Ca2+) and lead(II) ions (Pb2+), and you wish to selectively precipitate out the lead(II) ions only. Which of the following sodium salts would you choose in order to accomplish this selective precipitation?

 Predict the sign of ΔS with explanation for each process. (i) H2O (g)H2O (l) 

H2O (g)H2O (l) 

Rank from lowest to highest boiling point. To rank items as equivalent, overlap them. H2S H2Se H20

Balance the equation: NaCN + H₂SO₄ → Na₂SO₄ + HCN

What is the frequency of a photon with a wavelength of 781 nm. Report your answers to three significant digits.

The frequency is = _________ s^-1

What is the energy of a photon with a wavelength of 650 nm. Report your answers to three significant digits.

The energy is _________ J.

Below is the energy level diagram (not drawn to scale) representing the transitions made by an electron in a hydrogen atom that result in the observed lines of both the absorption and emission spectra. Some are in the visible region, and some are not.

4 different energy photons are represented (approximate wavelengths are given in parentheses):

infrared (~ 10e-4 m)

red (~ 10e-6 m)

blue (~ 10e-7 m)

ultraviolet (~ 10e-8 m)

Match the transition (a - h) with the photon described (approximate wavelengths are given in parentheses.) Your answer input should be a single, lower case letter.

(Please note: This is not a problem for which a calculator is required. Your knowledge of the Bohr model of the atom and the relative energies of transitions is all that is needed.)

Blue photon emission (~ 10^-7 m)