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Molecules, Compounds, and Chemical Equations

Molecules, Compounds, and Chemical Equations. Outline Chemical Bonds Introduction to Organic Molecules Percent Composition Empirical Formula Molecular Formula Balancing Chemical Equations. Chapter 3. Molecular View of Elements and Compounds. What is a formula unit?.

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Molecules, Compounds, and Chemical Equations

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  1. Molecules, Compounds, and Chemical Equations Outline Chemical Bonds Introduction to Organic Molecules Percent Composition Empirical Formula Molecular Formula Balancing Chemical Equations Chapter 3

  2. Molecular View of Elements and Compounds

  3. What is a formula unit?

  4. P4, S8, and Se8 are the polyatomic elements

  5. Combining Elements to make Compounds 2 H2 (g) + O2 (g) 2 H2O (l)

  6. Formation of Water from Its Elements

  7. Ionic vs. Molecular Compounds Propane – contains individual C3H8 molecules Table salt – contains an array of Na+ ions and Cl- ions

  8. How are chemical formulas represented?

  9. Examples of different molecule representations

  10. Chapter 3: Examples – Percent Composition, Empirical, Molecular Formulae • Citronellal, an aldehyde, has insect repellent properties. A sample was found to have 2.460 g carbon, 0.373 g hydrogen, and 0.329 g oxygen. • What is the percentage of carbon in the sample? • What is the molecular formula of citronellal? It’s molar mass is about 154 g/mol.

  11. Chapter 3: Examples – Empirical and Molecular Formula It is found that a sample of liquid bromine of mass 1.546 g reacts with fluorine gas to form 2.649 g of a bromine fluoride liquid. • Determine the empirical formula. • Write the balanced chemical reaction, if the molar mass is about 137 g/mol.

  12. Chapter 3: Examples – Empirical and Molecular Formula Salicylic acid, used in the synthesis of aspirin, has a mass composition of 60.87% C, 4.38% H, and 34.75% O. What is the formula of salicylic acid?

  13. Chapter 3: Examples – Empirical and Molecular Formula • Combustion of a 1.000 g sample of an organic compound known to contain carbon, hydrogen, and oxygen produces 2.360 g of carbon dioxide and 0.640 g of water. • What is the empirical formula? • The molar mass of the gas cyclopronanone is about 56 g/mol. Write the balanced combustion reaction. • What is the functional group for cyclopronanone?

  14. Chapter 3: Examples – Empirical and Molecular Formula Caffeine is made up of carbon, hydrogen, nitrogen, and oxygen atoms and has a molar mass of 194 g/mol. When 0.376 g of caffeine was burned 0.682 g of carbon dioxide, 0.174 g of water, and 0.110 g of nitrogen gases were formed. Determine the empirical and molecular formulas.

  15. Chapter 3: Examples – Empirical and Molecular Formula A compound containing Ca, S, C, and N was analyzed as follows. It’s formula mass is about 156 g/mol. • A 0.125 g sample was mixed with sodium carbonate until all of the calcium was converted to a 0.0800 g sample of calcium carbonate. • A 0.115 g sample was carried through a series of reactions until all of the sulfur was converted to 0.344 g of barium sulfate. • A 0.356 g sample was processed to liberate all of the nitrogen into 0.0775 g of ammonia. • Find the empirical and molecular formulae. • Name the compound.

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