Ch. 11 & 3  IMF & stoichiometry                   test     [90 points]                   AP Chem

For problems involving calculations, show your work in an organized manner, include relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer.              

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

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1.  What is the basis of adsorption chromatography (ignore the effects of the solvent in the mobile phase) ?   [10 points]

2.   The boiling point of HCl, HBr, and HI is 110 °C, - 66 °C, and 127 °C, respectively.  Rationalize the relative boiling point between  __.  [20 points]


a.  HCl versus HBr

b.  HCl versus HI

3.  Describe the basis of London IMF in a nonpolar compound.   [10 points]

4.  Determine the % yield in the reaction:  25.0 g N2   +  7.0 g H2   ->  23.0 g NH3 .   [15 points]

6.  Balance the following chemical equations using the lowest ratio of integers (as appropriate, enter “1”).  [15 points]

a.   ____  CH3 OH  +  ____ O2   ->  ___ CO2   +  ____ H2 O

b.  ___  NH3   +  ___ O2   ->  ___ NO  +  ___ H2 O

c.  ___  Cr  +  ___ O2   ->  ___ Cr2 O3

d.  ___  magnesium nitrate  +  ___ potassium phosphate  ->   ___  magnesium phosphate  + 

___  potassium nitrate


7.  Determine the molecular formula of a (hypothetical ?) compound containing carbon, hydrogen, and oxygen based on the following reaction:

1.00 g compound  +  excess O2   ->  1.784 g CO2   +  0.7297 g H2 O

The molar mass of the compound is 148 g / mole.  [20 points]

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Ch. 11 & 3  IMF & stoichiometry                   retest  [90 points]                   AP Chem

 

1.  If the yield = 85 % in the combustion of ethane:  C2 H6   + O2   ->  CO2   +  H2 O, in the presence of excess O2 , how much ethane would be needed to produce  5.0 g of water ?   [15 points]

2.   solve:   [10 points]

a.  15.0 g of sodium carbonate =  __ moles of sodium carbonate

b.  25.0 millimoles of potassium peroxide  =  __ grams of potassium peroxide

3.   The combustion of 1.50 g of a compound (containing carbon, hydrogen, and chlorine) in excess oxygen produced 3.52 g CO2 .  In another experiment, a 1.00 g sample of the compound with excess silver nitrate produce 1.27 g AgCl.  What is the empirical formula of the compound ?   [20 points]

4.   What is the relative vapor pressure of CH3 Cl versus CH3 Br ?  Rationalize your response; if it is ambiguous, then elaborate.  [10 points]

5.   surface tension.  [10 points; you might be able to answer these questions without reading your textbook]

a.  rationalize the shape of the surface of water in a glass capillary tube.  [hint:  it’s an U-shape surface]

b.  rationalize “capillary action” – the upward flow of water in a small diameter glass capillary tube [hint:  see question 5a]

6.  Rationalize the slope (i.e. positive versus negative) between the solid – liquid interface in the phase diagram for  __.   [10 points]

a.  water

b.  carbon dioxide

7.  Rationalize the relative boiling point of water at sea level versus on a mountain top.  [10 points]

8.  old topic:   solve:  5.0  mm2 / second  =  __  cm2 / minute.   [5 points]