Spring 2017 CSUSM Chem 160 FINAL EXAM REVIEW PRACTICE (12 POINTS)
This practice review will be considered replacement points for the final exam. Chapter 12. Chemical Kinetics
1. What is the rate law for the reaction 2A + 2B + 2C products (0.5 pts)
Initial [A], M Initial [B], M Initial [C], M Rate (M/s)
0.273
0.763
0.400
3.0
0.819
0.763
0.400
9.0
0.273
1.526
0.400
12.0
0.273
0.763
0.800
6.0
a) rate = k[A][B][C]
b) rate = k[A][B] 2[C] c) rate = k[A]3[B]4[C]2
d) rate = k[A]2[B]2[C]2 2. Consider the reaction: 2 NO + 2 H2 N2 + 2 H2O and the following data in order to answer the questions a-c.
(1.0 pts)
Exp Initial [NO] Initial [H2] d [NO dt 1 1.00 1.00 3.5 x 10-5 2 1.20 1.20 3 0.80 0.80 6.1 x 10-5
1.8 x 10-5 4
5 1.00 2.00 M•s-1
t 0 7.0 x 10-5
1.4 x 10-4 2.00
1.00
a) Determine the rate law for this reaction consistent with the above data. b) Determine the rate constant for this reaction consistent with the rate law you determined at a) 3. Initial rate data for the reaction follows. (0.5 pts)
Experiment
[N2O5]0
1
0.15 M
2
0.20 M
3
0.20 M
What is the rate law for this reaction? Dr. Gonzales 2N2O5(g) 4NO2(g) + O2(g)
[O2]0
Initial Rate in M·s–1
0.30 M
0.60 M
0.30 M 46
61
61 Page 1 Spring 2017 CSUSM (A) rate = k[N2O5] (C) rate = k[N2O5]1.3[O2]2 (B) rate = k[[N2O5]2 D) rate = k[N2O5]2[O2] Chem 160 4. Nitrogen and oxygen gas react to produce poisonous nitrogen monoxide. Assume the activation energy for the forward reaction is 270 kJ. ( 2.0 pts)
N2 (g) + O2(g) → 2 NO(g) ΔH = +90 kJ/mol
a. In the box provided, sketch and completely label
a potential energy diagram for this reaction. Be
sure to label the;
1. potential energy of the reactants
2. potential energy of the products
3. enthalpy (heat) of reaction
4. activated complex
5. activation energy of the forward and reverse
reactions.
b. Classify the forward reaction as endothermic or
exothermic. Justify your choice. c. Consider the activation energy of the forward
reaction. Is the forward reaction fast or slow? Why? d. What is the value of Ea for the reverse reaction? ________________________ e. What is the relationship between H, Ea,fwd and Ea,rev________________________ Chapter 13 & 14. Equilibrium & Acids, Bases
5. What is the Ka of a weak acid (HA) if a 0.19M solution has a pH of 4.52? (1.0 pts) Dr. Gonzales Page 2 Spring 2017 CSUSM Chem 160 Chapter 15: Applications of Aqueous Equilibria
6. A solution is prepared by mixing 2.00 g propionic acid, HC3H5O2 (MW = 74 g/mol, Ka = 1.3 x 10-5) with 0.45 g of
solid NaOH (MW = 40 g/mol) in water to make 500.0 mL. (2.0 pts)
a) Write the complete chemical equation including phases for the neutralization reaction that occurs. Use on of the following arrows: or or , to show the equilibrium of the reaction. b) Write any electrolytes in the above neutralization products in their dissociated form. c) Calculate moles of NaOH added: d) Calculate moles of propionic acid added: e) Determine the pH of the resulted solution? 5. A 35.00 mL sample of 0.2500 M HCl is titrated with 0.440 M NaOH. Calculate the pH after the following amounts of
base have been added. (1.5 pts)
a. 10.00 mL;
b. 20.00 mL;
c. 30.00 mL
Show work: Dr. Gonzales Page 3 Spring 2017 CSUSM Chem 160 6. A volume of 10.0 mL of 0.10 M H3PO4 was titrated with 0.10 M NaOH. The pH response to addition of
various amounts of NaOH is shown in the graph below. Answer the questions A-F. (1.5 pts) A. The titration curve shown above describes the: a. titration of a triprotic base.
b. titration of a diprotic acid. c. titration of a triprotic acid.
d. titration of a diprotic base. B. Use letters A & B to label on the graph the first two half titration points and read the value of pKa1 and the value of
pKa2? _________
C. Use letters C& D to label on the graph the first and the second equivalence points?
D. At what pH would you want your indicator color change to occur at in order to titrate to the first equivalence
point?____
E. At point A the ratio of [H3PO4]/[H2PO4–] is: a) 1 b) 2 c) 3 d) 4 F. When more than 15.0 mL of titrant have been added in the titration curve above, the pH can be determined by
assuming there is:
a) a weak base in solution.
c) a buffer with H2PO4- and HPO42-.
b) excess strong acid added to solution.
d) excess strong base added to solution.
7. The addition of solid Na2SO4 to an aqueous solution in equilibrium with solid BaSO4 will cause: (Circle one) (0.25
pts)
a) no change in [Ba2+] in solution.
c) precipitation of more BaSO4.
b) more BaSO4 to dissolve.
D) an increase in the Ksp of BaSO4.
8. If two salts, AX and BX2, have the same Ksp values of 4.0 × 10–12 at a given temperature, then
(Circle one) (0.25 pts)
a) their molar solubilities in water are the same.
b) the salts are more soluble in 0.1 M NaX than in water.
c) the molar solubility of AX in water is less than that of BX2.
d) addition of NaX will not affect the solubilities of the salts.
Dr. Gonzales Page 4 Spring 2017 CSUSM Chem 160 Chapter 16. Thermodynamics
9. Consider the reaction of decomposition of calcium carbonate, (CaCO 3(s)) to form calcium oxide (CaO(s) and CO2(g)
under standard conditions and 25.0°C. (1.5 pts)
Compound
∆fG° / kJ/mol
∆Hf°/kJ/mol
S°/J/(K•mol)
CaCO3(s)
-1129.1
-1207.6
91.7
CO2(g) -394.4 -393.5 213.6 CaO(s) -603.3 -634.9 38.1 a) Write the balanced chemical equation for this reaction. b) What is the enthalpy change of reaction per gram of calcium carbonate? Give your final answer in J/g. c) Is this process spontaneous under standard conditions? Answer this question with calculation using two methods
(prove that free energy of the system is negative and entropy of universe positive). Dr. Gonzales Page 5

 

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