Arkansas State University Department of Chemistry and Physics

a)  selenium trioxide

b)  chromium(III) fluoride pentahydrate

c)  hydrobromic acid

d)  actinium(III) sulfite

e)  ammonium oxalate

2.  Give the formula from the name for each:

a)  Fe₂(SO₄)₃

b)  P₂S₅

c)  Ru₂C

d)  HOCl

e)  Mn₂O₃

3.   State the law of multiple proportions:  if two elements combine to form more than one compound and the mass of one element is constant, the ratio of the mass of the second element is a simple fraction or whole number.

State the law of definite proportions: in a compound, the ratio of the masses is constant for any sample.

4.  Given the following equation:

a)  balance the equation:    4 Al₂O₃    +  9 Fe  g  3 Fe₃O₄    +  8 Al

b)  describe the type of reaction  metal displacement

c)  determine the Fe:Al₂O₃ mole ratio 9:4

5.  How would you prepare 75 mL of a 0.56 M solution of Ba(NO₃)₂ ?
(0.075 L)(0.56 M) = 0.042 mol Ba(NO₃)₂

(0.042 mol) (261.3 g mol^-1) = 11.0 g Ba(NO₃)₂

dissolve 11.0 g Ba(NO₃)₂ in distilled water to a total volume of 75 mL of solution

6.  How would you prepare 1.2 L of a 6 M H₂SO₄ solution if you start with a 18 M H₂SO₄ solution? M₁V₁ = M₂V₂
(6 M)(1.2 L)/ (18 M) = 0.4 L

slowly pour 400 mL of 18 M H₂SO₄ into distilled water, then dilute with distilled water until the total volume of the solution is 1.2 L.  Always add acid to water.  This reaction is exothermic.

7.  Write the electronic configuration for each of the following:

 a)  Ni - 1s²2s²2p⁶3s²3p⁶4s²3d⁸

 b)  As - 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p³

 c)  Li - 1s²2s¹

 d)  Rn - 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶

 e)  Au - 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s¹4f¹⁴5d¹⁰

8.  Give the number of valence electrons in each of the following:
 

a)  Cr - 1

b)  Al - 3

c)  Ti - 2

d)  B - 3

e)  Mn - 2

according to rules covered in General Chemistry class

9.  Draw an energy level diagram for Cr⁺² and describe its magnetic properties.

Cr⁺² - 1s²2s²2p⁶3s²3p⁶3d⁴ ; paramagnetic

10.  List the types of quantum numbers, what each of them represent and the possible values for each.  Be specific.
 

quantum numbers:	represent:	possible values:
n	size of shell	1 to infinity; integers
l	shape of subshell	0 to (n-1); integers
ml	direction of orbitals	+ l to -l, integers
ms	spin of the electron	+ 1/2

11.  Which would have the larger ionization energy, Na or P?  Why?  Define ionization energy.  Ionization energy is the energy needed to remove a single electron from an atom in the gas phase.  Phosphorus would have the higher ionization energy, being a smaller atom, the electrons are closer to the nucleus, more energy is needed to remove the electron.

12.  Which would be larger in size, C or C ^{- 4}? C ^{- 4} Why? more electrons in C ^{- 4}, less pull per electron from the nucleus and there is increase electron-electron repulsions.

13.  Of the five sets of quantum numbers listed below, 2 of them are not valid.  Circle the two incorrect sets of quantum numbers.
 

(4, 2, 0, +1/2)

(4, 4, 0, -1/2)

(5, 2, -2, -1/2)

(8, 7, -6, +1/2)

(4, 1, +2, -1/2)

14.  Draw the Lewis Dot Structure for each of the following:
 

a)  AsF5	b)  SiCl4	c)  SO32-	d)  AlH4-

15. Describe the expected angles for PF₃. less than the expected 109.5^o due to lone pair interactions with the three bonding pairs

16.  Describe the bonding in each of the following:  (ionic, polar covalent or covalent)
all are polar covalent

17.  For each of the following, give the electron arrangement (E.A.) and the molecular geometry (M.G.).
 

	E.A.	M.G.
a)   CO2	linear	linear
b)   BrF3	trigonal bipyramidal	t-shaped
c)   AsI3	Td	trigonal pyramidal
d)   SO2	trigonal planar	bent
e)   BrF4-	Oh	square planar

18.  Describe the bonding in CO₂.  Include a diagram showing orbital overlap.
2 s bonds, 2 p bonds

19.  Given two molecules, Br₂ and F₂, which has the higher boiling point?  Why?
Br₂ has the higher boiling point - larger molecule is more polarizable, greater London Forces means more energy is needed to separate the Br₂ molecules and convert the liquid into the gas phase.

20.  Write the equilibrium expression for each of the following:  Where possible, express both K_c and K_p.  (Assume each of these are equilibria equations)

 a)   2 NaN_{3 (s)}   g   2 Na _(s)   +    3 N_{2 (g)}

K_c = [N₂]³ ; K_p = P_N2³

 b)   4 NH_{3 (g)}  +  5 O_{2 (g)} g    4 NO _(g)  +   6 H₂O _(g)

K_c = [NO]⁴[H₂O]⁶ _/[NH₃]⁴[O₂]⁵  ; K_p = P_NO⁴P_H2O⁶_/P_NH3⁴P_O2⁵

21.  According to Le Chatelier's Principle,

 a)  what effect would the addition of Cl^- have on the equilibrium below?

   CoCl₂   +   2 Cl^-    g      CoCl₄^2-
shift to the right
 b)  what effect would the addition of Ag⁺ have on the equilibrium in problem 21a if the Ag⁺ precipitates as AgCl? shift to the left

22. Calculate the pH of a 0.002 M NaOH solution.

pOH = - log[OH^-];  pOH = 2.7
pH = 14 - pOH; pH = 11.3

23.  For each pair of acids, circle the strongest one.
 

a.	HCl	HBr
b.	HCl	H2S
c.	H2SO3	H2SO4
d.	CH4	H2O
e.	H3PO4	H3AsO4

24.  For the following salts, define the resulting solutions as either acidic, basic or neutral.

 a) NH₄Br  acidic

 b) Na₂SO₄   neutral

 c) KF   basic

 d) sodium acetate  basic

 e) CaCl₂ neutral

25.  Calculate the equilibrium concentrations of a 0.2 M HF solution. Ka = 7.1 x 10^-4

K_a = [H⁺][F^-]_/[HF] = x²/0.2 = 7.1 x 10^-4
solve for x; x = 1.2 x 10^-2
[H⁺] = x = 1.2 x 10^-2
[F^-] = x = 1.2 x 10^-2
[HF] = 0.2 - x = 0.2 - 1.2 x 10^-2 = 1.88 x 10^-1
 

26.  Define a basic oxide: forms a basic solution when placed in water; acidic oxide:forms an acidic solution when placed in water; and an amphoteric oxide: behaves as either an acid or a base, depending on the reaction conditions.

27.  Write the K_sp expression for each of the following:

 a)  AgCl _(s)  g    Ag⁺_(aq)    +    Cl^- _(aq)

 K_sp = [Ag⁺][Cl^-]

 b)  Ag₂CO_{3 (s)}  g   2 Ag ⁺ _(aq)   +     CO₃^2- _(aq)

K_sp = [Ag⁺]²[CO₃^2-]

28.  Given the K_sp = 2.4 x 10^-4 for PbCl₂, determine if a precipitate will occur from mixing 0.5 L of 0.02 M NaCl solution with 0.5 L 0.02 M Pb(NO₃)₂ solution.

Q = [Pb⁺²]_o[Cl^-]_o²

[Cl^-]_o = (0.5 L)(0.02 M)/ 1 L = 0.01; [Pb⁺²]_o = (0.5 L)(0.02 M)/ 1 L = 0.01

Q = 1.0 x 10^-6 ; K_sp > Q, no precipitate will form

29.  Determine the K_sp for Ag₂SO₄ if the molar solubility is 1.5 x 10^-2 M.
Ag₂SO_{4 (s)}  g   2 Ag ⁺ _(aq)   +     SO₄^2- _(aq)
                                 2x                        x
x = 1.5 x 10^-2

K_sp = [Ag⁺]²[SO₄^2-] = (2x)²(x) = 1.35 x 10^-5
 
 

30.  Fill in the blanks.

 List the Group V cations Ba⁺², Ca⁺², Mg⁺²

 Reagent used to precipitate Group III cations hydroxide ions

 Reagent used to precipitate Group I cations chloride ions

31.  Write the equation that relates DG^o with the equilibrium constant K.  Which way does the equilibrium lie if K < 1?

  DG^o = - RT lnK; reactants are favored

32.  Determine the E for the Co⁺²/Co and Pb⁺²/Pb half-cells if the [Co⁺²] = 0.50 M and the [Pb⁺²] = 0.25 M.

E_cell = E^o_cell - 0.0591/ n (logQ) = 0.14 V
Q = [Co⁺²]/[Pb⁺²]

Pb⁺²  +  Co  g   Co⁺²  +  Pb;  2 e^- process; n = 2
 

Co  ---->  Co+2	+0.28 V
Pb+2  ---->  Pb	-0.13 V
Eocell =	+0.15 V

33.  Will I₂ react with Pb?  Explain.  If it does react, what is (are) the product(s)?  Give the balanced equation.  yes, Pb is above and to the right in the standard reduction tables.
Pb _(s) + I_{2 (aq)}  g   PbI_{2 (s)}

34.  Write the solubility rules.
1. Group IA, NH₄⁺ - soluble
2. NO₃^-, ClO₃^-, ClO₄^- - soluble
3. OH^- - insoluble except Group IA, NH₄⁺, Ba⁺², Ca⁺² (ss)
4. Cl^-, Br^-, I^- - soluble except Pb⁺², Ag⁺, Hg₂⁺²
5. CO₃^2-, PO₄^3-, S^2- - insoluble except Group IA, NH₄⁺
6. SO₄^2- - soluble except Ba⁺², Pb⁺², Hg⁺²; slightly soluble: Ag⁺, Ca⁺²

35.  What are VSEPR rules and why are they important? VSEPR sets priorities for the placement of electron pairs around a central atom.  These rules allow for the prediction of the correct molecular geometry for a molecule based on its Lewis Dot Structure.

36.  Define an Arrhenius acid/ base, Bronsted-Lowry Acid/ base and a Lewis acid/ base.
Arrhenius acid:  contains H and donates H⁺ when placed in water; Arrhenius base: contains OH and donates OH^- when placed in water
Bronsted-Lowry acid: donates H⁺; Bronsted-Lowry base: accepts H⁺
Lewis acid: electron pair acceptor;  Lewis base: electron pair donor

37. What is K_sp and what information does it give? solubility product, it tells how soluble a solid compound is.  The smaller the number, the lower the solubility (generally)

38.  What is K_a and pK_a?  What does the magnitude of the numbers tell us?  K_a - Acid dissociation constant and pK_a = -log K_a.  The smaller the K_a, the weaker the acid.  The larger the pK_a, the weaker the acid.