Ch. 6 & 9 moles & stoichiometry                    retest  [70 points]                   honors Chem


For problems involving calculations, show your work in an organized manner, include any 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.


                                                                                                Signature:  ___________________


1.  solve  [15 points]


a.  0.00850 mole sulfur dioxide = __ g


b.  8.05 * 1018 C8H10N4O2 (caffeine)  =  ___ g


c.  0.0888 mole C3H8  =  __ C3H8 molecules



2.  Based on the following hypothetical experimental data, determine the empirical formula of BaxCly(H2O)z.  [25 points]


# g cpd  +  test tube before heating =  7.20

# g cpd + test tube after heating =  6.89

# g test tube =  5.70


add excess AgNO3 to cpd after heating, then filter suspension


# g filter paper =  2.5

# g filter paper + precipitate =  3.32 



3.  Solutions of sodium carbonate and silver nitrate react to form silver carbonate and sodium nitrate.  A solution containing 5.00 g of sodium carbonate is mixed with one containing 5.00 g of silver nitrate.  After the reaction is complete, the solutions are evaporated to dryness, leaving a mixture of salts.  How many grams of sodium carbonate, silver nitrate, silver carbonate, and sodium nitrate are present after the reaction is complete ? [20 points]



4.  Benzene, C6H6, reacts with bromine, Br2, to form bromobenzene, C6H5Br.   [10 points]


            C6H6  +  Br2  à  C6H5Br  +  HBr


a.  what is the theoretical yield of bromobenzene in this reaction when 40.0 g of benzene reacts with 75.0 g of bromine ?



b.  if the % yield = 83 %, then what was the experimental yield of bromobenzene ?