CHEM 110 - Introduction to Inorganic Chemistry

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Exam I – Part 2                                                 September 20, 2002

Instructions:     

1.      You have a total period of 2.0 hours to complete this examination.  You may take breaks as you desire.  Break times are not counted in the 2.0 hour time period. 

2.      Once you start the exam, you are not allowed to look at any chemistry reference material whatsoever from this year or years past.  You may not look at any textbooks or notes from any chemistry class past or present. 

3.      You may not communicate with anyone else in any form concerning this exam or the material that it covers or represents.

4.      If you have a question, the instructor is the only person allowed to address the question.  You may contact me at the Smith building until 4 PM (x-4218) September 20, 2002.  I will be back in my office at 7AM, Sept 23, 2002.

5.      You may work on this exam only in the Lyon Building, the Smith Building, the library, or a designated study area.  If you live off campus, you may work at home.

6.      The Lyon Honor Code is in force.

7.      The exam is due in my office (#11 Smith Building) no later than 9 AM Monday, September 23, 2002. 

8.      You may turn in your exams in class or on my desk. 

9.      I will accept no late exams – see the course syllabus for rare exceptions.

 

NOTES:          I have 55 of these exams to grade.  Please write and draw your answers as neatly as possible.

                        You may use the periodic table found on the inside cover of your textbook.

                        SIGNIFICANT FIGURES count on this exam.   

 

 

1.  (3 pts.)        A chemist treats 33.15 g of an oxide of uranium is treated with fluorine to produce oxygen and 44.53 g of uranium hexafluoride UF6.  What is the empirical formula of the oxide?

                                   

                        NOTE:  SHOW YOUR WORK – AN ANSWER WITHOUT THE WORK IS WORTH ZIPPO (i.e., NOTHING).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.  (3 pts.)        Talc, the principle ingredient in baby powerd, has the following elemental composition:  19.24% Mg, 0.53% H, 29.56% Si, and 50.67% O by mass.  What is the empirical formula for talc?

 

 

 

 

 

 

 

 

 

3.  (3 pts.)        Calcium nitrate and ammonuim fluoride react to form calcium fluoride and dinitrogen monoxide, and water vapor.  What mass of each substance is present after 16.8g of Ca(NO3)2  and 17.50g of NH4F react completely?

 

 

 

 

 

4.      (3 pts.)  This is a two-part question dealing with the following reaction:

 

4 NH3  +  5 O2  à  4NO  +  6 H2O

 

(a)  If 7.00 grams of ammonia and 14.0 grams of oxygen react to form nitric oxide

and water as shown in the equation below, which one of the two reactants limits

the amount of product formed? 

 

(b)  How much NO is formed?

 

 

                                   

 

 

 

 

 

 

5.  (3 pts.)        Answer the following questions about significant figures:

 

(a)    What does the word “exactly” mean in the following statement:  “there are exactly 2.54 cm in one inch”?

 

 

 

(b)   The answer to the expression 2.1 x 3.44 x 0.59321 reads 4.2853490 on the calculator display.  How should the answer be reported?

 

 

 

 

(c)    If a jar of jelly beans contains approximately 5400 jelly beans, what is the appropriate way to report this number scientifically?