Chem 1010 Tutorials
Tutorial 4A – Empirical and Molecular Formulas
Fall 2013
1.
A sample of a tin and chlorine compound with a mass of 2.57 g was found to contain 1.17 g of tin. What is
the compound’s empirical formula?
2.
A compound responsible for the odor of garlic has a molar mass of 146 g/mol. A 0.650 g sample of the
compound contains 0.321 g of carbon, 0.044 g of hydrogen, and 0.285 g of sulfur. What is the molecular
formula of the compound?
3.
A white smelly solid compound had the following elemental analysis:
22.89% carbon
0.96% hydrogen
76.15% bromine
(by mass)
a)
Determine the empirical formula of the compound.
–1
b)
If the molar mass was found to be approximately 316 g·mol , what is the molecular formula of
the compound?
4.
Caffeine has a molar mass of 194.19 g/mol and the following percent composition:
49.48% carbon
5.19% hydrogen
28.85% nitrogen
16.48% oxygen
What is the molecular formula for caffeine?
5.
A very smelly substance has the elemental analysis:
C - 24.97%;
H - 8.38%;
S - 66.65 %
Calculate the empirical formula of the substance.
6.
A pure compound was isolated from a soil sample obtained near an industrial site. The elemental ratios
of the solid were determined by analysis to be: C 0.1975 H 0.1269 Cl 0.2116
a)
What is the empirical formula (smallest whole number ratio) of this compound? Show work.
b)
With which of the following contaminant compounds are these ratios consistent?
i) chlordane (C10H6Cl8)
ii) DDT (C14H9Cl15)
iii) tetrachloro PCB (C12H6Cl4)
iv) toxaphene (C10H10Cl8)
Answers:
1. SnCl4
2. C6H10S2
3. a) C2HBr
b) C6H3Br3
4. C8H10N4O2
5. CH4S
6. a) C14H9Cl15
b) DDT