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Chemistry 301 - MIDTERM EXAM #1

Wednesday, October 6, 2004, 9:00 am

Explain your answers whenever possible, Calculators are permitted.

Worth 20 points (20% of course)

1) (3 points) Briefly answer the following:

a) What is the difference between alkalinity and basicity?

b) Briefly describe two properties of water that are a unique consequence of cooperative

hydrogen bonding.

c) Why is CO2more soluble in water than you would predict based on Henry's Law alone?

2) (3 points) What does it mean when we say that water is "hard"? What visible effects are

found when hard water is boiled? Why? What is this due to?

3) (4 points) Given a choice of typical, naturally occurring ligand atoms (list them), which do

you think is/are the most likely candidates for Cd+2

and Ca+2

, respectively, to bind with?

Explain why.

4) (4 points) At pH 7.3, what is the dominant form of total CO2(CO2)? What is the ratio of

[HCO3-] to [CO3

-2]? If CO2is measured to be 2.1 x 10

-3M, what is [CO3

-2]?

5) (6 points) What is the predicted Mn+2

concentration in equilibrium with MnCO3(s) at pH8.0, in a solution with a carbonate alkalinity of 1.0 x 10

-3eq./L?

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Potentially useful data:

Reaction Kind of

Constant

Value

CO2(aq)HCO3-+ H+ pKa1 6.35

HCO3-CO3-2+ H+ pKa2 10.33

CO2(g)

CO2(aq) pKH 1.47H2S(g)H2S(aq) pKH 0.99

H2S(aq)HS-+ H+ pKa1 7.02

HS-S-2+ H+ pKa2 13.9

H3PO4H2PO4-+ H+ pKa1 2.17

H2PO4-HPO4-2+ H+ pKa2 7.21

HPO4-2PO4-3+ H+ pKa3 12.32

Fe(OH)3(s)+ 3H+Fe+3+ 3H2O pKsp -3.96

Fe(OH)2(s) + 2H+Fe+2+ 2H2O pKsp -12.9

Pb(OH)2(s)Pb+2+ 2OH- pKsp 19.79

PbCO3(s)Pb+2+ CO3-2 pKsp 12.82CaCO3(s)Ca+2+ CO3-2 pKsp 8.35

MnCO3(s)Mn+2+ CO3-2 pKsp 9.3

AlPO4(s)Al+3+ PO4-3 pKsp 21.0

Al+3+ OH-Al(OH)+2 pKf1 -9.0

Al+3+ 2OH-Al(OH)2+ pf2 -18.7

Al+3+ 3OH-Al(OH)3(s) pf3 -27.0

Al+3+ 4OH-Al(OH)4- pf4 -33.0

H3(NTA)H++ H2(NTA)- pKa1 1.66

H2(NTA)-H+ + H(NTA)-2 pK

a22.95

H(NTA)-2H++ (NTA)-3 pKa3 10.28

Ca+2+ (NTA)-3Ca(NTA)- pKf -8.2

Mn+2+ (NTA)-3Mn(NTA)- pKf -8.7

Fe+2+ (NTA)-3Fe(NTA)- pKf -9.6

Pb+2+ (NTA)-3Pb(NTA)- pKf -11.4

Al+3+ (NTA)-3Al(NTA) pKf -13.4

Fe+3+ (NTA)-3Fe(NTA) pKf -17.9

For the reaction: aA + bBcC + dD,

K = [C]c[D]d at equilibrium, Q = [C]c[D]d at any given moment_______ _______

[A]a[B]b [A]a[B]b

Henrys Law: [X(aq)] = KHPX

[X(aq)] = concentration of gas X in water

KH= Henrys Law constant at specific T,P,S

PX = partial pressure of gas X in solution at equilibrium