percent composition and chemical formulas

End Show© Copyright Pearson Prentice Hall

Slide 1 of 40

Percent Composition and Chemical Formulas

It helps to know the percents of the components in a shirt because they affect how warm it is, whether it will need to be ironed, and how it should be cleaned. You will learn how the percents of the elements in a compound are important in chemistry.

10.3



>

Slide 2 of 40

The Percent Composition of a Compound

The Percent Composition of a Compound

How do you calculate the percent by mass of an element in a compound?

10.3

End Show

Slide 3 of 40

© Copyright Pearson Prentice Hall


> The Percent Composition of a Compound

The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%.

10.3

End Show

Slide 4 of 40




Percent Composition from Mass Data

The relative amounts of the elements in a compound are expressed as the percent composition or the percent by mass of each element in the compound.

10.3


SAMPLE PROBLEM

Slide 5 of 40

End Show

10.9


SAMPLE PROBLEM

Slide 6 of 40

End Show

10.9


SAMPLE PROBLEM

Slide 7 of 40

End Show

10.9


Slide 8 of 40

End Show

Practice Problems for Sample Problem 10.9

End Show

Slide 9 of 40




Percent Composition from the Chemical Formula

10.3


SAMPLE PROBLEM

Slide 10 of 40

End Show

10.10


SAMPLE PROBLEM

Slide 11 of 40

End Show

10.10


SAMPLE PROBLEM

Slide 12 of 40

End Show

10.10


Slide 13 of 40

End Show


End Show

Slide 14 of 40




Percent Composition as a Conversion Factor

You can use percent composition to calculate the number of grams of any element in a specific mass of a compound.

10.3

End Show

Slide 15 of 40




Propane (C3H8) is 81.8% carbon and 18% hydrogen. You can calculate the mass of carbon and the mass of hydrogen in an 82.0 g sample of C3H8.

10.3



>

Slide 16 of 40

Empirical Formulas

Empirical Formulas

What does the empirical formula of a compound show?

10.3

End Show

Slide 17 of 40



> Empirical Formulas

The empirical formula gives the lowest whole-number ratio of the atoms of the elements in a compound.

The empirical formula of a compound shows the smallest whole-number ratio of the atoms in the compound.

10.3

End Show

Slide 18 of 40



> Empirical Formulas

Ethyne (C2H2) is a gas used in welder’s torches. Styrene (C8H8) is used in making polystyrene.

These two compounds of carbon have the same empirical formula (CH) but different molecular formulas.

10.3


SAMPLE PROBLEM

Slide 19 of 40

End Show

10.11


SAMPLE PROBLEM

Slide 20 of 40

End Show

10.11


SAMPLE PROBLEM

Slide 21 of 40

End Show

10.11


SAMPLE PROBLEM

Slide 22 of 40

End Show

10.11


Slide 23 of 40

End Show




>

Slide 24 of 40

Molecular Formulas

Molecular Formulas

How does the molecular formula of a compound compare with the empirical formula?

10.3


Slide 25 of 40


> Molecular Formulas

The molecular formula of a compound is either the same as its experimentally determined empirical formula, or it is a simple whole-number multiple of its empirical formula.

10.3

End Show

Slide 26 of 40



> Molecular Formulas10.3

Methanal, ethanoic acid, and glucose all have the same empirical formula—CH2O.

End Show

Slide 27 of 40



> Molecular Formulas10.3


SAMPLE PROBLEM

Slide 28 of 40

End Show

10.12


SAMPLE PROBLEM

Slide 29 of 40

End Show

10.12


SAMPLE PROBLEM

Slide 30 of 40

End Show

10.12


SAMPLE PROBLEM

Slide 31 of 40

End Show

10.12


Slide 32 of 40

End Show



Slide 33 of 40

Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

10.3 Section Quiz.

10.3.


Slide 34 of 40

End Show

1. Calculate the percent by mass of carbon in cadaverine, C5H14N2, a compound present in rotting meat.

a. 67.4% C

b. 58.8% C

c. 51.7% C

d. 68.2% C

10.3 Section Quiz.


Slide 35 of 40

End Show

2. Which of the following is NOT an empirical formula?

a. NO2

b. H2N

c. CH

d. C3H6

10.3 Section Quiz.


Slide 36 of 40

End Show

10.3 Section Quiz.

3. Determine the molecular formula of a compound that contains 40.0 percent C, 6.71 percent H, and 53.29 percent O and has a molar mass of 60.05 g.

a. C2H4O2

b. CH2O

c. C2H3O

d. C2H4O

percent composition and chemical formulas

Documents