Chem271-s13 Hour Iiia

8/12/2019 Chem271-s13 Hour Iiia

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CHEM271 - S13 Hour Exam IIIA

(10) 1) Complete the following decay equations:

a) 241Am (Z=95) ! 237Np (Z=93) + ________

b) 53Fe (Z=26) !"++ ________

c)111Ag (Z= 47)!111Cd (Z = 48) + _______

d) 96Mo (Z = 42) + 2H !n + _______

e) 252Cf (Z = 98) !132Sn (Z = 50) + ______ + 4n

(5) 2) For the following reaction coordinate diagram, clearly label the rate determining step, theactivation energy Eafor the reaction, #H of the reaction, the location of any intermediate and

show how the diagram might change with the use of a catalyst.

(5) 3) What is the osmotic pressure of a solution made from 25.6 mg of insulin (molar mass =

5990 g/mol) in 10.0 mL of an aqueous solution at 25oC? Express your answer in mm Hg.

CHEM271- S13 Hour IIIA p. 4


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(10) 4) Find the energy released in the fission of 1.00 g of 240Pu (Z = 94) according to240Pu!128Sn + 109Ru + 3n

240Pu = 240.0538075 amu128Sn = 127.910535 amu

109Ru = 108.9132016 amun = 1.00866490 amu

(5) 5) Find the molality of a solution that is 1.50 M in sulfuric acid (molar mass = 98.08 g/mol) if

the density of the solution is 1.105 g/mL at 25oC?

(10) 6) a) Using the data below, determine the rate law for the following reaction.

H2PO4-(aq) + OH-(aq) ! HPO4-(aq) + H2O(l)

Exp. [H2PO4-] (M) [OH-] (M) Initial Rate (M/min)

1 0.0030 0.00040 0.0020

2 0.0030 0.00080 0.0080

3 0.0090 0.00040 0.0060

b) What is the rate constant with the correct units?



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(5) 7) If the vapor pressure of pure ethanol is 100.5 mm Hg at 35.0 oC, what is the vapor pressure

of a solution made by dissolving 25.0 g of sucrose (molar mass = 342.3 g/mol) in 500.0 g of

ethanol (molar mass = 46.07 g/mol).

(5) 8) Po-209 is an alpha emitter with a t1/2= 102 years. What is the activity in Bq of 1.00 ng

sample of 209Po?

(10) 8) Use the proposed mechanism to answer the following questions

1) NO2(g) + SO2(g) ! NO (g) + SO3(g) Slow (k1)

2) 2NO (g) + O2(g) !2NO2(g) Fast (k2)

3) 2SO2(g) + O2(g) !2SO3(g) Fast (k3)

a) What is the overall reaction?

b) What is the intermediate(s) (if any)?

c) What is the catalyst (if any)?

d) Which step is the rate determining step?

e) What is the rate law for the reaction?



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(5) 9) What is the molecular weight of acetaminophen if the boiling point elevation #Tb= 4.5 oC

when 6.33 g of acetaminophen is dissolved in 25.0 g of methanol. Kbof methanol = 2.7 oC/m.

(10) 10) Use the following data table to determine the rate law for the disappearance of H2O2.

Time (s) [H2O2] ln[H2O2] 1/[H2O2]

0 1 0 1.00

120 0.91 -9.43E-02 1.10

300 0.78 -2.48E-01 1.28

600 0.59 -5.28E-01 1.69

1200 0.37 -9.94E-01 2.70

1800 0.22 -1.51 4.55

b) What is the rate constant for the reaction with the appropriate units?


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Chem271-s13 Hour Iiia