Chapter 2 Lecture Problems

Protons, Neutrons and Electrons

1. ¹H Hydrogen
2. ²H Deuterium
3. ³H Tritium
4. ¹⁴C
5. ¹⁹F
6. ²⁶⁶Mt
7. ²⁷⁷112
8. Neon

Atomic Weight

1. Chlorine

Isotope	Exact Mass	Abundance	% abundance
35	34.9688530	999	75.5
37	36.9659	324	24.5

2. Bromine

Isotope	Exact Mass	Abundance	% abundance
79	78.9183320	999	50.5
81	80.9163	978	49.5

3. Mercury

Isotope	% Abundance
196	0.146
198	10.2
199	16.4
200	23.13
201	13.22
202	29.8
204	6.85

Mole Calculations

1. Calcluate the number of moles in 12.0 g of C, 24.0 g of C, 48.0 g of C, 1.0 g of C.
2. Calculate the mass of 1 mole of C, 2, mole of C, 3 mole of C, 0.01 mole of C.
3. Calculate the number of carbon atoms in 1 g of C.

Molecular Weight

1. Calculate the molecular weight of:
   1. NaCl
   2. H₂O
   3. CFCl₃
   4. C₂H₆O

2. Beer has about 10. grams of ethanol (C₂H₆O), how many moles of ethanol? How many ethanol molecules? How many carbon atoms? How many hudrogen atoms? How many oxygen atoms?

3. One cup of Coffee has about 50 mg of caffeine (C₈N₄O₂H₁₀). How many moles of caffeine? How many Moles of carbon? How many moles of nitrogen? How many moles of oxygen? How many moles of hydrogen?

4. It is possible to measure a picomole of CCl₄. How many grams is this?

5. It is possible to measure an attomole of sodium. How many grams is this? How many atoms?

6. A friend of mine from graduate school worked on a laser fluorescence experiment that measured a special dye compound at a concentration of 10 yoctomoles (10^-24). If the dye has a molecualr weight of 300 g/mole, how many grams of dye is this? How many dye atoms?

7. In a laboratory experiment, it is routine to measure out 0.0154 mole of sodium chloride. How many grams is this?

8. Calculate the percent mass of each element for the given chemical formula:
   1. NaCl
   2. H₂O
   3. CFCl₃

Emperical Formula

1. What is the emperical formula of a salt. 100.0000 grams of salt is analyzed and found to contain:
   1. 39.3374 grams of sodium
      
   2. 60.6626 grams of chloride

2. What is the emperical formula of an alcohol. 69.8457 grams of AN alcohol is analyzed and found to contain:
   1. 41.9124 grams carbon
      
   2. 9.3234 grams hydrogen
      
   3. 18.6100 grams oxygen

3. What is the molecular formula of the alcohol if:
   1. MW = 60.05 grams/mole
      
   2. MW = 120.10 grams/mole

4. 1 asprin tablet contains 325 mg of acetylsalicylic acid (C₉H₈O₄, see page 220 in textbook for structure).
   1. How many moles of asprin, carbon, hydrogen, and oxygen are in a single tablet?
   2. How many atoms(molecules) of asprin, carbon, hydrogen and oxygen are in a single tablet?
   3. What is the percent composition of acetylsalicylic acid?

5. Pamoic acid is one compound I study extensively. Based on the 3D model determine the following:
   1. The Molecular Formula
   2. The Emperical Formula
   3. The Molecular Mass
   4. The Emperical Mass
   5. The number of moles in 1.34 mg of pamoic acid
   6. The number of moles of C, H, and O in 1.34 mg of pamoic acid
   7. The number of molecules in 1.34 mg of pamoic acid
   8. The mass of 9.35 nano moles of pamoic acid

6. The elemental analysis for another compound I will discuss is given below.

   Elemental Analysis Results

   Element	Percent Composition
   Carbon	59.96
   Hydrogen	13.42
   Nitrogen	0
   Oxygen	26.62
   Chlorine	0

   1. What is the Emperical Formula for this compound?
   2. The Mass Spectrometry analysis of this compound shows that it has a molecular weight of 60 u. What is the Molecular Formula?
   3. Based upon the emperical formula this compound could be 1-propanol or 2-propanol (courtesy Dave Woodcock).
      • From the CRC Handbook of Chemistry and Physics the density of 1-propanol is 0.8035 and the density of 2-propanol is 0.7855.
      • Measure the mass of a beaker (69.2543 g). Use a 50.000 mL pipet to add the unknown liquid to the beaker and measure the mass (109.4293 g).
      • What can you determine?

Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

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Last Updated Friday, May 25, 2001 2:10:36 PM