Ch. 6, 9 & 11 light, mole, & stoichiometry                             [50 points]                   Chemistry

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.

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1. find the average atomic mass based on the following (hypothetical) data.   [15 points]

 

atomic mass (amu)

% abundance

45 Ca

44.983

3.00

40 Ca

39.971

87.00

38 Ca

37.897

 ?

2. mass – mole conversion problems. [10 points]


a. 10.0 g Na3 PO4 = ___ moles of Na3 PO4

b. 2.5 millimoles K2 CO3 = ___ grams of K2 CO3

3.  light [10 points]


a. if frequency = 2.6 * 10 15 Hz, the energy = ___.

b. if wavelength = 217 nm, then energy = __.

4.  How many grams of aluminum would be needed to produce 100. mL of water in the following reaction ? [15 points; assume there is excess NH4 ClO4 ]


Al + NH4 ClO4   -->  Al2 O3 + AlCl3 + NO + H2 O