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Chemistry 135
Exam 1
January 6, 2006
Name __________________
SHOW YOUR WORK. NO WORK, NO CREDIT
INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS
Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers.
EQUATIONS AND CONSTANTS YOU MAY NEED
particles
M
1mL = 1cm 3 D =
c = λν E = hν
mole
V
J•s
J
C p (H 2 O) = 4.184
- q lost = q gained q = mC p ∆T
photon
g • deg
N o = 6.022x10 23
h = 6.626 x 10 -34
q rxn
∆G = ∆H - T∆S 1 torr = 1 mm Hg K = C + 273.15
mole lim reagent
L • atm
L • torr
mL • torr
J
= 62.36
= 62360
= 8.314
R = 0.08206
K • mole
K • mole
K • mole
K • mole
P1 V1 P2 V2
lb
=
1 atm = 760 torr = 14.7 2 = 101.325 kPa PV = nRT
T1
T2
in
moles solute
∆T = ikm πV = inRT
PTotal = P1 + P2 +... m =
kg solvent
∆H =
pH = - log[H + ]
K w = 100
. x10 −14
rate = k[A] x [B] y ...
2nd order
∆G = - nFE
K w = K a K b = [H + ][OH − ] pK w = pH + pOH
[A]
ln 2
1st order ln
= - kt or ln[A] = - kt + ln[A ] 0 t 1/2 =
[A ] 0
k
1
1
= kt +
[A]
[A] 0
AX2
AX3
AX2E
AX4
AX3E
AX2E2
linear
trigonal planar
bent
tetrahedral
trigonal pyramid
bent
coul
Ea ⎛ 1⎞
⎜ ⎟
R ⎝ T⎠
coul
J = coul • V
s
mole e
RT
0.05916
E = Eo ln Q E 25o = E o ln Q
nF
n
∆G o = - RT ln K eq
E cell = E red - E ox
k = Ae − E a / RT or ln k = ln A -
AX5
AX4E
AX3E2
AX2E3
F = 96485.31
-
trigonal bipyramid
see saw
T
linear
square planar family not included
A =
AX6
AX5E
AX4E2
AX3E3
AX2E4
octahedral
square pyramid
square planar
T
linear
I PLEDGE ON MY HONOR THAT DURING THE EXAM I HAVE NEITHER GIVEN NOR RECEIVED
ASSISTANCE NOR HAVE I SEEN ANY DISHONEST WORK.
Signed __________________________________________________________________________
If you feel you can’t sign this, contact the instructor (e-mail or in person)
1
Circle the correct answer.
1.
(2 pts) Which one of the following is amphiprotic in aqueous solution?
a) HI
2.
d) HI
b) solution 3
c) solution 4
d) none
b) H2PO4-1
c) HPO4-2
d) PO4-3
(2 pts) The following pictures represent equal volumes of aqueous solutions of three acids HA (A = X, Y, or Z);
water molecules have been omitted for clarity. Arrange the conjugate bases (A-1 = X-1, Y-1, or Z-1) in order of
increasing base strength.
a) Z-1 < X-1 < Y-1
6.
c) HNO2
(2 pts) What is the conjugate base of H2PO4-1?
a) H3PO4
5.
b) NaOH
(2 pts) The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.
Unshaded spheres represent H atoms and shaded spheres represent A-1 ions. (K+1, H3O+1, OH-1, and solvent H2O
molecules have been omitted for clarity.) For which solution(s) is pH = pKa?
a) solution 2
4.
d) HSO4-1
(2 pts) When the following salts are dissolved in separate samples of water at the same concentrations, which
solution will have the lowest pH?
a) NaCl
3.
c) H2PO4-1
b) NH3
b) X-1 < Z-1 < Y-1
c) Y-1 < Z-1 < X-1
d) Z-1 < Y-1 < X-1
(2 pts) What is the net ionic equation for the neutralization reaction of a weak acid with a weak base?
a) H3O+1 (aq) + OH-1 (aq) X 2 H2O (l)
b) HF (aq) + NH3 (aq) X NH4+1 (aq) + F-1 (aq)
c) H3O+1 (aq) + NH3 (aq) X NH4+1 (aq) + H2O (l)
d) HF (aq) + OH-1 (aq) X H2O (l) + F-1 (aq)
2
7.
(2 pts) What is the pH of an aqueous solution of acetic acid that contains 4.5 x 10-3 M hydronium ions.
a) 2.35
8.
b) 7.00
d) can’t be determined
(2 pts) Which of the following aqueous mixtures is a buffer?
a) 1 M HF
9.
c) 11.65
b) 1 M HNO2 + 1 M KNO2
c) 1 M NaCN
d) 1 M HClO2 + 1 M Na2SO3
(3 pts each) Name the following compounds.
a.
PbCrO4
________________________________
b.
HClO4
________________________________
10. (3 pts each) Write the formula for each of the following compounds.
a.
tin (II) phosphite
________________________________
b.
nitrous acid
________________________________
11. (3 pts each) How you would distinguish between the following pairs of compounds or ions? Assume the
compounds are solids and the ions are in aqueous solution. STATE WHAT REAGENT YOU WOULD ADD AND
WHAT YOU WOULD SEE FOR EACH SPECIES THAT RESULTS IN THE DISTINCTION.
a.
b.
c.
CdCl2 and AgCl
K2CrO4 and KNO3
Hg2Cl2 and PbCl2
12. (10 pts) When KClO is dissolved in water, the resulting solution is basic. Starting with the molecule, write the stepwise, net ionic reactions that show how this compound produces hydroxide in aqueous solution.
13. (12 pts) A solid mixture contains one or more of the following salts:
AgNO3
PbI2
Hg2SO4
The solid is completely soluble in water. When an excess of concentrated ammonia is added to the solution, no
precipitate forms. Which compounds are present, absent, and undetermined. Explain your reasoning.
14. (5 pts) Why is vinegar kept in the safety island?
15. (12 pts) Determine the Ka for nitrous acid if a a 0.010 M solution that has a pH of 2.70?
16. (12 pts) What is the pH of a solution containing 0.100 M NaCN and 0.250 M HCN? Ka for HCN is 6.2 x 10-10.
17. (12 pts) What volume of 0.500 M HNO3 is needed to titrate 60.00 mL of 0.500 M Ca(OH)2 solution to the
equivalence point?
Chemistry 135
Exam 2
Name __________________
January 13, 2006
SHOW YOUR WORK. NO WORK, NO CREDIT
INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS
Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers.
Silver Group: Ag, Hg, Pb
Copper-Arsenic Group: Cu, Hg, Pb, As, Sb, Bi, Sn, Cd
Aluminum-Nickel Group: Ni, Fe, Co, Mn, Al, Cr, Zn
Barium-Magnesium Group: Na, K, Mg, Ca, Ba, NH4+1
3
Circle the correct answer.
1.
(2 pts) The following pictures represent solutions of CuS, which may also contain ions other than Cu+2 and S-2 which
are not shown. Gray spheres represent Cu+2 ions and dotted spheres represent S-2 ions. If solution (1) is a saturated
solution of CuS, which of solutions (2)-(4) are unsaturated?
a) only (2)
2.
b) only (3)
c) only (4)
d) (3) and (4)
(2 pts) What is the line notation that represents the following cell reaction?
Fe(s) + Cu(NO3)2(aq) ! Fe(NO3)2(aq) + Cu(s)
a) Fe | Fe+2 || Cu+2 | Cu
b) Cu+2 | Cu || Fe+2 | Fe
c) Fe | NO3-1 || NO3-1 | Cu
d) Fe | Fe+2 || Cu+2, H+1 | H2 | Pt
3.
(2 pts) Which aqueous metal ion will reduce Ag+, but not Cu+2?
a) Fe+2
4.
b) Mn+2
c) Sn+2
d) Fe+3
(2 pts) Aluminum requires relatively little protection from corrosion because
a) aluminum is protected by cathodic protection.
b) the reduction potential for Al+3/Al is very low.
c) aluminum has little tendency to react with oxygen.
d) the oxidation of aluminum produces a hard,
relatively impenetrable film of Al2O3.
5.
(2 pts) Consider the following standard reduction potentials under standard conditions,
Al+3 + 3e- ! Al
I2 + 2e- ! 2 I-1
E° = -1.66 V
E° = +0.54 V
a) I2 is a stronger reducing agent than Al+3.
b) Al is a stronger reducing agent than I-1.
c) I-1 is a stronger reducing agent than Al.
d) Al+3 is a stronger reducing agent than I2.
6.
(2 pts) For a galvanic cell that uses the following two half-reactions, how many moles of Pb(s) are oxidized by one
mole of Cr2O7-2?
Cr2O7-2 + 14 H+1 + 6 e- ! 2 Cr+3 + 7 H2O
Pb ! Pb+2 + 2 e-
a) 1
7.
c) 6
d) 2
(2 pts) Which metal exhibits the highest oxidation state in its compounds?
a) As
8.
b) 3
b) Mn
c) Cr
(2 pts) In the cell reaction for a dead battery,
4
d) Zn
a) E is negative and ∆G is negative.
b) E is negative and ∆G is positive.
c) E is zero and ∆G is zero.
d) E is zero and ∆G is positive.
9.
(2 pts) Which transition element is difficult to oxidize with hydronium ion?
a) Cu
b) Mn
c) Co
d) Cr
10. (3 pts each) Name the following compounds.
a.
HgSO4
________________________________
b.
[CrCl2Br2]-1
________________________________
11. (3 pts each) Write the formula for each of the following compounds.
a.
hydrosulfuric acid
________________________________
b.
triamminetriiodocobalt (III)
________________________________
12. (10 pts) Balance the redox reaction which occurs in basic solution.
CrO4-2 + C2H6O ! Cr+3 + C2H4O2
13. (6 pts) What is the equilibrium constant for the reaction 2 Ag+1 + Cu ! 2 Ag + Cu+2?
14. (3 pts each) How you would distinguish between the following pairs of compounds or ions? Assume the
compounds are solids and the ions are in aqueous solution. STATE WHAT REAGENT YOU WOULD ADD AND
WHAT YOU WOULD SEE FOR EACH SPECIES THAT RESULTS IN THE DISTINCTION.
a.
b.
Bi+3 (aq) and Cd+2 (aq)
Al(OH)3 and Zn(OH)2
15. (10 pts) What is the pH of a solution produced by mixing 50.00 mL of 0.2500 M NH4Cl with 32.00 mL of 0.1500
M KOH. Ka for NH4+ = 5.6 x 10-10.
16. (7 pts) Adequate corrosion resistance in a particular application requires 60 mg Cr/cm2. What current is necessary
to electrodeposit such a layer of chromium on a 5 cm x 10 cm piece of metal in 1.00 minute in a plating bath of
0.5 M Cr2(SO4)3?
17. (10 pts) What is the pH of the solution in the half cell || H+1 | O3 (0.5 atm), O2 (0.25 atm) | Pt, if the half cell produces
1.90 V?
18. (7 pts) A copper-arsenic group unknown was treated with the group reagent in the usual manner. A yellow
precipitate was formed that was completely insoluble in excess ammonium sulfide. What ions in the copper-arsenic
group are present, absent, and undetermined? EXPLAIN YOUR REASONING. A list of the metals in each group
is given on page 1.
19. (7 pts) BaSO4 and BaSO3 are both insoluble ionic compounds. Explain why BaSO3 readily dissolves in concentrated
HCl, but BaSO4 does not. Use stepwise, net ionic reactions to illustrate your explanation.
20. (7 pts) What is the pH of a saturated solution of nickel hydroxide if the solution has [Ni+2] = 1.00 x 10-7 M? This
solution contains unknown components besides nickel hydroxide that could be affecting the pH. Ksp for nickel
hydroxide is 1.6 x 10-16.
Chemistry 135
Exam 3
5
Name __________________
January 20, 2006
SHOW YOUR WORK. NO WORK, NO CREDIT
INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS
Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers.
Silver Group: Ag, Hg, Pb
Copper-Arsenic Group: Cu, Hg, Pb, As, Sb, Bi, Sn, Cd
Aluminum-Nickel Group: Ni, Fe, Co, Mn, Al, Cr, Zn
Barium-Magnesium Group: Na, K, Mg, Ca, Ba, NH4+1
Circle the correct answer.
1.
(2 pts) Which of the following high spin complexes are diamagnetic?
[Cd(NH3)4]+2
[Fe(CN)6]-4
[Mn(CN)6]-3
a) [Mn(CN)6]-3
2.
b) [Cd(NH3)4]+2
[FeF6]-3
c) [Mn(CN)6]-3, [Fe(CN)6]-4, [FeF6]-3
d) [FeF6]-3
(2 pts) Which of the ligands below are bidentate ligands?
C O
N C
S
H2N
O
O
H2C C
carbon monoxide
(a)
a) all are bidentate
3.
c) (c) and (d)
d) none are bidentate
b) (1) and (2)
c) (2) and (4)
d) (1) and (3)
c) F-1, fluoro
b) NH3, ammonia
d) H2O, aquo
b) Sb
c) Al
d) Fe
c) FeS
d) all of them
(2 pts) Which sulfide is soluble in concentrated HCl?
a) CuS
7.
b) (a) and (b)
O
oxalate
(d)
(2 pts) Which of the following metals will not dissolve in concentrated HCl?
a) Sn
6.
glycinate
(c)
(2 pts) Which ligand when bonded to a metal would be incorrectly named?
a) CO, carbonyl
5.
O
(2 pts) Consider the following isomers of [Co(NH3)4Br2]+1. The black sphere represents Co (central atom/ion), gray
spheres represent NH3, and unshaded spheres represent Br. Which are trans isomers?
a) (3) and (4)
4.
C C
O
thiocyanate
(b)
O
b) As2S5
(2 pts) Which complex ion is colorless?
6
a) [FeF6]-3
8.
c) [Cr(OH)4]-1
d) all are colored
c) [Sn(OH)4]-2
d) HCl
(2 pts) Which species will reduce Bi+3 to Bi0?
a) Fe+2
9.
b) [Cu(NH3)4]+2
b) [Sn(OH)6]-2
(2 pts) Which compound, when dissolved in water, will form a precipitate with Mg+2 but not with Ba+2?
a) NH4H2PO4
b) NaOH
c) (NH4)2S
d) H2SO4
10. (2 pts) An alloy dissolves in concentrated HNO3 leaving a white precipitate. Which metal could be in the
precipitate?
a) Ag
b) Fe
c) Al
d) Sn
11. (2 pts) Consider the following ethylenediamine complexes. The black sphere represents Co (central atom/ion), gray
connected spheres represent ethylenediamine, NH2CH2CH2NH2, and unshaded spheres represent Br. Which
complexes are chiral?
a) (1), (2) and (4)
b) (1), (2) and (3)
c) (1), (3) and (4)
d) (2), (3) and (4)
12. (3 pts each) Name the following:
a.
[Cu(en)2]+2
________________________________
b.
[Cu(CN)2]-1
________________________________
13. (3 pts each) Write the formula for each of the following:
a.
pentacarbonylnickel(0)
________________________________
b.
copper(II) hexacyanoferrate(II)
________________________________
14. (10 pts) Consider the reduction half cell: ||Cu(OH)2 (sat’d)|Cu. If the Ksp of Cu(OH)2 is 1.6 x 10-19, what is the
voltage for this half cell?
15. (8 pts) Balance the following redox reaction in acid solution.
H2C2O4
+
MnO4-1
!
Mn+2
+
CO2
16. (8 pts) What is/are the possible hybrid(s) for the complex [Ru(NH3)6]+3? Ru is element 44. Show the orbital (box)
notation for the central ion and identify the orbitals used in each complex.
17. (10 pts) What is the pH of the solution produced when 25.00 mL of 0.1000 M HC2H3O2 is mixed with 15.00 mL
of 0.1500 M Ba(OH)2?
18. (10 pts) [PtCl2Br(CN)]-2 forms a low spin, square planar complex. Draw the possible isomers for this ion. Identify
the type of isomer for each (linkage, ionization, diasteriomer, enantiomer).
7
19.
Mn
Cr
Fe
Ni
As
Ag
Cu
(10 pts) An alloy that may contain only the metals listed above completely dissolved in concentrated HCl. Addition
of excess NH3 produced a colorless solution and a rust-red precipitate. The precipitate was completely insoluble
in excess NaOH. Which metals are present, absent, and undetermined? EXPLAIN YOUR REASONING.
20. (10 pts) How many hours must a constant current of 50.0 amps be passed through an electrolytic cell containing
aqueous 1M Na2Cr2O7 to produce 3.00 moles of chromium metal?
8