Chem. 4B Exam. I. (Rate of RXN; Chemical Equilibrium; Acid/Base) 09/14/04
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Chem. 4B
Exam. I 09/14/04
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Problem / Pts1 (10 pts)
2 (10 pts)
3 (10 pts)
4 (10 pts)
5 (10 pts)
6 (10 pts)
7 (15 pts)
8 (10 pts)
9 (15 pts)
Total (100 pts)
1) ( 10 pts ) Suppose the following data is obtained for the reaction
2 NO(g) + 2 H2(g) à N2(g) + 2 H2O(g)
[NO]o (mol/L) [H2]o (mol/L) Rate (mol L-1 s-1)
0.10 0.20 0.0150
0.10 0.30 0.0225
0.20 0.20 0.0600
a) Write the rate law for this reaction.
b) Calculate the rate constant (be sure to include the units!!!)
2) The equilibrium constant KC = 190 at 1000 K, for the following reaction.
CO(g) + 3 H2(g) à H2O(g) + CH4(g)
The initial concentrations are: [CO]o = 0.025 M, [H2]o = 0.045 M, [H2O]o = 0.025 M and [CH4]o = 0.046 M.
a. (5 pts ) Calculate the reaction quotient QC.
b. (5 pts ) In what direction does the reaction proceed in order to reach equilibrium? Circle the answer.
left right neither, the reaction is already at equilibrium
3) Consider the following reaction at equilibrium:.
N2O4 (g) à 2 NO2 (g)
The value of KP is 0.90 at 120oC and 3.2 at 150oC.Predict how the equilibrium will shift by the following changes. Circle the correct answer. (10 pts )
c. The temperature is decreased.
left right no shift
d. An inert gas, argon, is added.
left right no shift
e. The volume is decreased.
left right no shift
4) An excess of solid NH4Cl is added to a container filled with 1.5 atm of ammonia gas at 340oC.Calculate the pressures of HCl and NH3 at equilibrium. (10 pts )
HCl (g) + NH3 (g) à NH4Cl (s) KP = 4.0 at 340oC
5) Circle the correct answer for each of the following questions. (10 pts )
f. Which is the strongest acid?
H2S H2O H2CO3
g. Which is the strongest base?
ClO– H2O C5H5N
h. Which salt, when dissolved in water, will produce the most basic solution?
KCl KCN KNO2 KNO3
i. Which of the following 0.1 M solutions will have the lowest pH?
NaNO3 NaOH HF KF
6) In the first order reaction, A à products, the initial concentration [A]o = 0.500 M and after 15.0 minutes, [A] = 0.150 M. At what time will [A] = 0.200 M? (10 pts )
7) The reaction
2A +B à C
has the following proposed mechanism:
Step 1: A + B D (fast equilibrium)
Step 2: D + B à E (slow)
Step 3: E + A à C + B (fast)
a. If step 2 is the rate-determining step, then the rate of formation of C should equal? (Show the works) (10 pts)
b. What are the intermediates in this mechanism? (5 pts)
8) The rate constant for a reaction increases from 10.0 sec1 to 100. sec1 when the temperature is increased from 300. K to 400. K. What is the activation energy for the reaction in kJ/mole? (10 pts )
9) In a 5.00 L container at 450oC, H2 reacts with I2 to produce HI. At equilibrium the partial pressures of H2 and I2 are both 1.25 atm, and the partial pressure of HI is 10.00 atm. If 1.50 atm of HI is added to this mixture, calculate the partial pressures of H2, I2 and HI after equilibrium is reestablished.(15 pts )
Ka / Acid / BaseName / Formula / Formula / Name
Large / Perchloric acid / HClO4 / ClO4 / Perchlorate ion
3.2 109 / Hydroiodic acid / HI / I / Iodide
1.0 109 / Hydrobromic acid / HBr / Br / Bromide
1.3 106 / Hydrochloric acid / HCl / Cl / Chloride
1.0 103 / Sulfuric acid / H2SO4 / HSO4 / Hydrogen sulfate ion
2.4 101 / Nitric acid / HNO3 / NO3 / Nitrate ion
------/ Hydronium ion / H3O+ / H2O / Water
5.4 102 / Oxalic acid / HO2C2O2H / HO2C2O2 / Hydrogen oxalate ion
1.3 102 / Sulfurous acid / H2SO3 / HSO3 / Hydrogen sulfite ion
1.0 102 / Hydrogen sulfate ion / HSO4 / SO42 / Sulfate ion
7.1 103 / Phosphoric acid / H3PO4 / H2PO4 / Dihydrogen phosphate ion
7.2 104 / Nitrous acid / HNO2 / NO2 / Nitrite ion
6.6 104 / Hydrofluoric acid / HF / F / Fluoride ion
1.8 104 / Methanoic acid / HCO2H / HCO2 / Methanoate ion
6.3 105 / Benzoic acid / C6H5COOH / C6H5COO / Benzoate ion
5.4 105 / Hydrogen oxalate ion / HO2C2O / O2C2O22 / Oxalate ion
1.8 105 / Ethanoic acid / CH3COOH / CH3COO / Ethanoate (acetate) ion
4.4 107 / Carbonic acid / H2CO3 / HCO3 / Hydrogen carbonate ion
1.1 107 / Hydrosulfuric acid / H2S / HS / Hydrogen sulfide ion
6.3 108 / Dihydrogen phosphate ion / H2PO4 / HPO42 / Hydrogen phosphate ion
6.2 108 / Hydrogen sulfite ion / HS / S2 / Sulfite ion
2.9 108 / Hypochlorous acid / HClO / ClO / Hypochlorite ion
1.7 109 / pyridinium / C5H5NH+ / C5H5N / Pyridine
6.2 1010 / Hydrocyanic acid / HCN / CN / Cyanide ion
5.8 1010 / Ammonium ion / NH4+ / NH3 / Ammonia
5.8 1010 / Boric acid / H3BO3 / H2BO3 / Dihydrogen carbonate ion
4.7 1011 / Hydrogen carbonate ion / HCO3 / CO32 / Carbonate ion
4.2 1013 / Hydrogen phosphate ion / HPO42 / PO43 / Phosphate ion
1.8 1013 / Dihydrogen borate ion / H2BO3 / HBO32- / Hydrogen borate ion
1.3 1013 / Hydrogen sulfide ion / HS / S2 / Sulfide ion
1.6 1014 / Hydrogen borate ion / HBO32 / BO33 / Borate ion
------/ water / H2O / OH / Hydroxide
- Strong acid are listed at the top left hand corner of the table and have Ka values >1
- Acid with values less than one are considered weak.
- The strong bases are listed at the bottom right of the table and get weaker as we move to the top of the table.
Chem. 4B Exam. I. (Rate of RXN; Chemical Equilibrium; Acid/Base) 09/14/04
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