CHM1045
Fall 2000
Dr. Michael Blaber
Name_______________________________SS#_________________________
Exam #1 100 points total
Friday September 29 2000
1. For the following substances, state whether they are most likely a pure substance, a heterogenous mixture, or a homogenous mixture (8 points)
Note: 2 points each a) Tap water homogenous mixture b) Beach sand heterogenous mixture c) Copper wire pure d) A suspiciously cheap "gold" ring sold at the University center by some guy named
"Rainbow" homogenous mixture
2. Given the following information write the complete chemical symbol (i.e. complete with appropriate superscripts) for each element or ion (8 points)
Note: 2 points each: 1 for symbol, 1/2 for each superscript
Number of
Neutrons
Number of
Electrons
Number of Protons Symbol
13 12 12 25 Mg
19 18 17 36 Cl -
6
35
2
27
5
29
11 B 3+
64 Cu 2+

3. Given the following chemical symbols for an atom or ion, write down the number of protons, neutrons and electrons (8 points)
Note: 1 point for correct protons, 1/2 point each for correct neutrons and electrons
Chemical symbol Number of Protons Number of Number of
Neutrons Electrons
18 O 28 10 10
40 Ca 2+
40 Ar
20
18
20
22
18
18
131 I 53 78
4. Write down the chemical formula for an ionic compound of the following combinations of metals and nonmetals (8 points)
Note: 2 points each. Putting non-metal first is counted as incorrect. a) Sodium and Sulfur
Na
2
S b) Calcium and Chlorine
CaCl
2 c) Aluminum and Oxygen
Al
2
O
3 d) Potassium and Bromine
KBr
54

5. Provide the names for the following chemical compounds or ions (8 points)
Note: 2 points each a) HClO
Hypochlorous acid b) H
2
SO
4
Sulfuric acid c) IO
4
-
Periodate, or Periodate ion d) SO
4
2-
Sulfate, or Sulfate ion
6. Draw chemical structures (i.e. use lines to indicate bonds between atoms , and show all atoms ) for the following organic molecules or functional groups (8 points)
Note: 2 points each a) Butane
H H H H
H C C C C H
H H H H b) Cycloheptane
H
H H
H
H
C
H
C C
H
H C C
H
H C C
H
H
H H c) Draw an alcohol functional group (use the letter 'R' to represent the organic part(s) of the molecule)
R-OH or R-O-H d) Draw a carboxylic acid functional group (use the letter 'R' to represent the organic part(s) of the molecule)
O O
R C C
O H or
R
OH

7. Determine the percentage by mass of C, H and O in propanol (C
3
H
7
OH; or C
3
H
8
O)
(8 points)
Note: 2 points for correct amu or formula mass. 2 points each for correct %
From the formula provided, one molecule of propanol would have a mass of:
(3*12.0) + (8*1.01) + (1*16.0) amu = 36.0 + 8.08 + 16.0 = 60.1 amu
The mass contribution from C would be:
36.0/60.1 = 0.609 x 100 = 59.9%
The mass contribution from H would be:
8.08/60.1 = 0.120 x 100 = 13.4%
The mass contribution from O would be:
16.0/60.1 = 0.271 x 100 = 26.6%
8. If 37.8g of propanol is combusted, how many grams of carbon dioxide is produced?
Be sure to include the balanced chemical equation for the combustion of propanol as part of your answer (12 points)
The balanced chemical equation for the combustion of propanol would be:
C
3
H
7
OH + 9 /
2
O
2

3CO
2
+ 4H
2
O or
2C
3
H
7
OH + 9O
2

6CO
2
+ 8H
2
O
Note: 4 points for correct balanced equation
37.8g of propanol would be equal to:
37.8g * (1mole/60.1g) = 0.629 moles
Note: 2 points for correct number of moles
The stoichiometry of the balanced equation is such that for every mole of propanol combusted, 3 moles of CO
2
are produced. Therefore:
0.629 moles propanol combusted * (3CO
2
/1propanol) = 1.89moles CO
2
Note: 2 points for correct number of moles of CO
2
The molecular mass of CO
2
is:
(1*12.0) + (2*16.0) = 44.0 amu, or 44 grams/mole
Note: 2 points for correct amu or formula mass for CO
2
Thus, converting moles of CO
2
to grams:
1.89 moles CO
2
* (44grams/mole) = 83.2 grams CO
2
produced
Note: 2 points for correct grams

9. If 48.7 grams of magnesium chloride is dissolved in 4.35 L of water, what is the resulting molarity of the magnesium chloride solution? (6 points)
Note: 2 points for correct formula
Magnesium chloride would have an empirical formula of MgCl
2
Note: 1 point for formula mass
Therefore, the formula mass would be:
(1*24.3) + (2*35.5) = 95.3 amu, or 95.3 grams/mole
Note: 1 point for number of moles
The number of moles in 48.7 grams would therefore be:
48.7 grams * (1 mole/95.3 grams) = 0.511 moles
Note: 2 points for correct molar conc
The resulting molar concentration of the solution would be:
0.511 moles/4.35L = 0.117 molar
10. Indicate whether the following ionic compounds are most likely soluble or insoluble in aqueous solution (8 points)
Note: 2 points each a) NaBr
Soluble a) NH
4
OH
Soluble a) AgCl
Insoluble a) Mg(OH)
2
Insoluble

11. Write the balanced molecular equation and the net ionic equation for the neutralization reaction between magnesium hydroxide, Mg(OH)
2
, and hydrochloric acid,
HCl (10 points)
The unbalanced equation would be:
Mg(OH)
2
+ HCl

MgCl
2
+ H
2
O
Note: 5 points for balanced equation
The balanced equation would be:
Mg(OH)
2
+ 2HCl

MgCl
2
+ 2H
2
O
The ionic equation would be:
Mg 2+ + 2OH + 2H + + 2Cl -

Mg 2+ + 2Cl + 2H
2
O
Note: 5 points for balanced net equation
The resulting net ionic equation would be:
Mg 2+ + 2OH + 2H + + 2Cl
2OH + 2H +

Mg 2+ + 2Cl + 2H

2H
2
O
2
O
12. What are the oxidation numbers assigned to the following atoms of each element?
(8 points)
Note: 2 points each (either all right or zero) a) CH
3
COOH
C = 0, O = -2, H = +1 b) ClO -
O = -2, Cl = +1 c) S
8
S = 0 d) H
2
O
H = +1, O = -2