CHM1045
Fall 2000
Dr. Michael Blaber

Name_______________________________SS#_________________________

1. For the following substances, state whether they are most likely a pure substance, a heterogenous mixture, or a homogenous mixture (8 points)

a) Tap water

homogenous mixture (i.e. will contain soluble ions in addition to water)

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 (i.e. probably an alloy and not pure gold, all metal alloys are homogenous mixtures0

2. Given the following information write the complete chemical symbol (i.e. complete with appropriate superscripts) for each element or ion (8 points)

3. Given the following chemical symbols for an atom or ion, write down the number of protons, neutrons and electrons (8 points)

4. Write down the chemical formula for an ionic compound of the following combinations of metals and nonmetals (8 points)

a) Sodium and Sulfur

Na₂S

b) Calcium and Chlorine

CaCl₂

c) Aluminum and Oxygen

Al₂O₃

d) Potassium and Bromine

KBr

5. Provide the names for the following chemical compounds or ions (8 points)

a) HClO

Hypochlorous acid

b) H₂SO₄

Sulfuric acid

c) IO₄^-

Periodate, or Periodate ion

d) SO₄^2-

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)

a) Butane

b) Cycloheptane

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)

7. Determine the percentage by mass of C, H and O in propanol (C₃H₇OH; or C₃H₈O) (8 points)

(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:

or

37.8g of propanol would be equal to:

37.8g * (1mole/60.1g) = 0.629 moles

The stoichiometry of the balanced equation is such that for every mole of propanol combusted, 3 moles of CO₂ are produced. Therefore:

0.629 moles propanol combusted * (3CO₂/1propanol) = 1.89moles CO₂

The molecular mass of CO₂ is:

(1*12.0) + (2*16.0) = 44.0 amu, or 44 grams/mole

Thus, converting moles of CO₂ to grams:

1.89 moles CO₂ * (44grams/mole) = 83.2 grams CO₂ produced

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)

Therefore, the formula mass would be:

(1*24.3) + (2*35.5) = 95.3 amu, or 95.3 grams/mole

The number of moles in 48.7 grams would therefore be:

48.7 grams * (1 mole/95.3 grams) = 0.511 moles

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)

a) NaBr

Soluble

a) NH₄OH

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:

12. What are the oxidation numbers assigned to the following atoms of each element? (8 points)

a) CH₃COOH

C = 0, O = -2, H = +1

b) ClO^-

O = -2, Cl = +1

c) S₈

S = 0

d) H₂O

H = +1, O = -2