Ap Chemistry Practice Test

Select Chapter 7 and 8 AP Problems

Directions:  Show all of your work in order to receive full credit.  If you have any questions, be sure to ask.

1.) 1980

(a) Write the ground-state electron configuration for an arsenic atom, showing the number of electrons in each subshell.

(b) Give one permissible set of four quantum numbers for each of the outermost electrons in a single As atom when it is in its ground state.

(c) Is an isolated arsenic atom in the ground state paramagnetic or diamagnetic? Explain briefly.

(d) Explain how the electron configuration of the arsenic atom in the ground state is consistent with the existence of the following known compounds: Na3As, AsCl3, and AsF5.

a) 1s2 2s22p6 3s23p6 4s23d104p3

b) for the two electrons in the 4s: 4, 0, 0, +1/2 and 4, 0, 0, – 1/2

for the three electrons in the 4p: 4, 1, -1, +1/2; 4, 1, 0, +1/2 and 4, 1, +1, +1/2

c) Paramagnetic. It has three unpaired electrons.

d)

Na3As – each Na gives up one electron to the As, the As has a complete octet and the sodium atoms are ionically bonded to the arsenic

AsCl3 – the three chlorines each have one half-filled orbital and the aresenic has three. So three covalent bonds are created and the As has one non-bonding pair to make a pyramidal structure.

AsF5 – fluorine is so eletronegative that it draws the two electrons of the non-bonding pair of AsCl3 into bonding. A 4d orbital is involved in the sp3d hydridization, yielding a trigonal bipyramidal shape.

2) 1981 The emission spectrum of hydrogen consists of several series of sharp emission lines in the ultraviolet (Lyman series). in the visible (Balmer series). and in the infrared (Paschen series, Brackett series, etc,) regions of the spectrum.

(a) What feature of the electronic energies of the hydrogen atom explains why the emission spectrum consists of discrete wavelengths rather than a continuum of wavelengths?

(b) Account for the existence of several series of lines in the spectrum. What quantity distinguishes one series of lines from another?

(c) Draw an electronic energy level diagram for the hydrogen atom and indicate on it the transition corresponding to the line of lowest frequency in the Balmer series.

(d) What is the difference between an emission spectrum and an absorption spectrum? Explain why the absorption spectrum of atomic hydrogen at room temperature has only the lines of the Lyman series.

a) 1 point

Quantized energy levels or discrete energies or wave properties of electron produce discrete energy states in a gas.

b) 2 points

The excited state atoms can relax to several lower energy states (see diagram in c).

Each final state energy level produces a separate series.