Name: __________________________________________________
Homework 2
**note – this is just a quick sample of naming – you are expected to be able to name compounds far
above and beyond these few examples (see your Nomenclature lab!)
1. Using the information in Table 1: “Densities of several elements” answer the following questions:
Density of element
0.0000899 g/mL
0.0001785 g/mL
2.26 g/mL
4.54 g/mL
8.90 g/mL
8.92 g/mL
11.35 g/mL
11.724 g/mL
13.546 g/mL
13.67 g/mL
18.95 g/mL
19.32 g/mL
21.45 g/mL
22.4 g/mL
22.6 g/mL
Name
Hydrogen
Helium
Carbon
Titanium
Cobalt
Nickel
Lead
Thorium
Mercury
Americium
Uranium
Gold
Platinum
Iridium
Osmium
Sym
H
He
C
Ti
Co
Ni
Pb
Th
Hg
Am
U
Au
Pt
Ir
Os
Atomic mass (amu)
1.008
4.003
12.01
47.87
58.93
58.69
207.2
232.04
200.59
243.06
238.03
196.97
195.08
192.22
190.23
Question 1: Looking at the mass of lead, how does its mass compare to mercury, gold, platinum, iridium,
and osmium – rank them by mass?
_____Pb_____> ____Hg_____> _____Au_____> ____Pt____ >____Ir____> ___Os____
Question 2: Looking at the density of lead, how does its density compare to those same elements? Rank
them by density
___Os____> ___Ir____> ___
Pt __>
___ Au ____ >____
Hg _____>
_____
Pb ______
Question 3: Therefore – can you simply look at the mass of a substance and say that it will have the
larger or smaller numerical density – explain your answer in grammatically correct sentences.
No, you cannot just look at the mass. Even though mass is in the numerator of the density
expression, density includes BOTH mass and volume. As shown above, sometimes the
heaviest mass object will not be the most dense. So even though Osmium has less mass, it
must have a much smaller volume resulting in a larger numerical density.
2. Name the following ionic compounds.
a. MgO ____magnesium
b. Al2S3 ____aluminum
c. Na2SO4 ____sodium
oxide__________________
sulfide_____________
sulfate____
3. Name the following covalent compounds:
a. NO2 ___nitrogen
b. SO2 _____sulfur
dioxide_____________________
dioxide____________________
c. PCl5 _____phosphorus
pentachloride___________
d. PCl3 _____phosphorus
trichloride___________
4. Determine the number of moles in 65.75 grams of Al2(SO4)3
Al: (2 * 26.98) = 53.96 + S: (3 * 32.07) = 96.21 + O: (12* 16.00) = 192.0 = 342.17 = 342.2 grams/moles
5. Determine the number of Aluminum ions in 99.85 grams of Al2(SO4)3
= 3.514 x 1023 Al+3 ions in the sample
6. Vanillic Acid, an oxidation product of the artificial flavoring vanillin, has the following elemental
analysis: C 57.14%, H 4.80%, O 38.06%. Determine the empirical formula.
1 mole C
= 4.757702 moles C/ 2.37875 = 2 C
12.01 grams C
57.14 grams C x
4.80 grams H x
1 mole H
= 4.752475 moles H/ 2.37875 = 1.997 = 2 H
1.01 grams H
38.06 grams O x
1 mole O
= 2.37875 moles O/ 2.37875 = 1 O
16.00 grams O
C2H2O - empirical
7. A 3.00 mg of aspirin was analyzed by combustion. Aspirin is known to contain 3 elements:
carbon, hydrogen, and oxygen (formula: CxHyOz). The results of the combustion analysis found
6.60 mg of CO2 and 1.20 mg of H2O.
a. Find the milligrams of C only in the 6.60 mg of CO2
b. Find the milligrams of H only in the 1.20 mg of H2O
c. Find the milligrams of O using the grams of C, H and the given mass of aspirin
d. Convert the milligrams into moles and determine the empirical formula
CxHyOz →
3.00 mg
6.60 mg CO2 x
1.20 mg H2O x
1g
1000 mg
1g
1000 mg
CO2 +
6.60 mg
H2O
1.20 mg
x
12.01 grams C 1000 mg C
1 mole CO 2
1mole C
x
x
x
= 1.80mg C
44.01 g CO 2 1 mole CO 2
1 mole C
1g C
x
1.01 grams H 1000 mg H
1 mole H 2 O
2 mole h
= 0.135 mg H
x
x
x
18.02 g H 2 O 1 mole H 2 O
1 mole H
1g H
mg C + mg H + mg O = total mg of sample
1.80 mg C + 0.135 mg H + x = 3.00 mg total
x = mg O = 1.07 mg
2.25 x 4 = 9
1.99 = 2 x 4 = 8
=1x4=4
Moles O are the smallest – divide everyone by moles O!
Since C is not a whole number we must turn all species into whole numbers
Empirical formula = C9H8O4