1. chemistry

2. Percent Composition and Chemical Formulas
10.3
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.

3. The Percent Composition of a Compound
10.3
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?

4. The Percent Composition of a Compound
10.3
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%.
Potassium chromate (K2CrO4 ) is composed of 40.3% potassium, 26.8% chromium, and 32.9% oxygen. Interpreting Diagrams How does this percent composition differ from the percent composition of potassium dichromate (K2Cr2O7), a compound composed of the same three elements?

5. The Percent Composition of a Compound
10.3
The Percent Composition of a Compound
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.

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10. for Sample Problem 10.9
Problem Solving Solve Problem 33 with the help of an interactive guided tutorial.

11. A compound is formed when 9.03 g Mg combines completely with 3.48 g N. What is the percent composition of this compound?

12. The Percent Composition of a Compound
10.3
The Percent Composition of a Compound
Percent Composition from the Chemical Formula

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17. for Sample Problem 10.10

18. The Percent Composition of a Compound
10.3
The Percent Composition of a Compound
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.

19. The Percent Composition of a Compound
10.3
The Percent Composition of a Compound
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.

20. Empirical Formulas What does the empirical formula of a compound show?
10.3
Empirical Formulas
Empirical Formulas
What does the empirical formula of a compound show?

21. 10.3
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.

22. 10.3
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.
Ethyne (C2H2), also called acetylene, is a gas used in welder’s torches. Styrene (C8H8) is used in making polystyrene. These two compounds have the same empirical formula. Calculating What is the empirical formula of ethyne and styrene?

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27. 10.3
Molecular Formulas
Molecular Formulas
How does the molecular formula of a compound compare with the empirical formula?

28. 10.3
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.

29. 10.3
Molecular Formulas
Methanal, ethanoic acid, and glucose all have the same empirical formula— CH2O.
Methanal (formaldehyde), ethanoic acid (acetic acid), and glucose have the same empirical formula. Applying Concepts How could you easily obtain the molar mass of glucose using the molar mass of methanal?

30. 10.3
Molecular Formulas

31. 10.3 Section Quiz.
10.3.

32. 10.3 Section Quiz.
1. Calculate the percent by mass of carbon in cadaverine, C5H14N2, a compound present in rotting meat.
67.4% C
58.8% C
51.7% C
68.2% C

33. 10.3 Section Quiz.
2. Which of the following is NOT an empirical formula?
NO2
H2N CH
C3H6

34. Concept Map 10
Concept Map 10 Solve the Concept Map with the help of an interactive tutorial.

35. END OF SHOW