CHEM 101L Chapter Notes - Chapter 5.2: Chemical Formula, Cyclopentane, Ethylene

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ceruleantortoise232

29 Oct 2016

School

CSUN

Department

Chemistry and Biochemistry

Course

CHEM 101L

Professor

Dr.Nguyen- Graff

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Document Summary

Chem 101: empirical and molecular formulas in multistructual compounds. Empirical formulas are the simplest whole number ratios of elements in a compound. For example if i had cyclcopentane (c5h12 [pentane] in a ring structure) then the empirical formula would be ch5 since the formula for cyclopentane is c5h10. So in this particular example cyclopentane has a molecular formula of c5h10 and has an empirical formula of ch5. It may seem confusing so here is an example of how to find empirical and molecular formulas: A compound weighs 440 g/mol, and they found it is composed 56. 34% phosphorus and 43. 66% oxygen. So in this problem we are given that the compound is 56. 34% phosphorus and. Whenever we are given a percentage, we always assume that there is 100 g of substance available since it is a percent (per every 100). So that means we 53. 34 g of phosphorus and 43. 66 g of oxygen if there is 100 g of substance.

Related Questions

Determine the empirical and molecular formulas of each of the following substances:

(a) Styrene, a compound substance used to make Styrofoam^® cups and insulation, contains 92.3% C and 7.7% H by mass and has a molar mass of 104 g/mol.

(b) Caffeine, a stimulant found in coffee, contains 49.5% C, 5.15% H, 28.9% N, and 16.5% O by mass and has a molar mass of 195 g/mol.

(c) Monosodium glutamate (MSG), a flavor enhancer in certain foods, contains 35.51% C, 4.77% H, 37.85% O, 8.29% N, and 13.60% Na, and has a molar mass of 169 g/mol.

Empirical formula of this compound is CH.

To determine the molecular formula, we need to find out how many times is molar mass higher than the mass of empirical formula:

Molecular formula is C₈H₈.

b) Empirical formula of caffeine:

Empirical formula of caffeine is C₄H₅N₂O. The sum of atomic masses from empirical formula is 97 g/mol.

Molecular formula of caffeine is 2 × empirical formula = C₈H₁₀N₄O₂

c) Empirical formula of MSG:

Empirical formula of MSG is C₅H₈NO₄Na. The sum of atomic masses of empirical formula is 169 g/mol, the same as molar mass. Empirical and molecular formula are identical.