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Molecules, Compounds and Chemical Equations

Molecules, Compounds and Chemical Equations. CHM 108 Suroviec Fall 2015. I. Hydrogen, Oxygen and Water. Hydrogen is an explosive gas Oxygen is a gas needed for burning Water is a very different molecule then either of these. II. Chemical Bonds.

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Molecules, Compounds and Chemical Equations

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  1. Molecules, Compounds and Chemical Equations CHM 108 Suroviec Fall 2015

  2. I. Hydrogen, Oxygen and Water • Hydrogen is an explosive gas • Oxygen is a gas needed for burning • Water is a very different molecule then either of these

  3. II. Chemical Bonds • Hold atoms together and are a result of interactions of the electrons of the atoms • 2 main types of bonds

  4. A. Ionic Bond • Since metals tend to lose electrons and nonmetals tend to gain electrons we often see when a metal and a nonmetal react to make an ionic bond

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  6. B. Covalent Bonds • Nonmetal to nonmetal and the electrons are shared

  7. III. Chemical Formulas • Chemical Formulas: indicate the elements present with the relative number of atoms or ions of each. • Empirical Formula: gives the relative number of atoms of each element in a molecule • Molecular Formula: gives actual number of atoms of each element in a molecule • Structural Formula: uses lines to show bonds

  8. IV. Atomic Level View • Atomic elements are those that exist in nature using single atoms of an element • Molecular elements exist as 2 or more atoms as a basic unit 3. Molecular compounds are composed of 2 or more covalently bound nonmetals 4. Ionic compounds are composed of a charged metal and nonmetal

  9. V. Ionic Compounds • Ionic compounds have an overall charge of zero and many elements form only 1 type of ion with a predicable charge

  10. VI. Molecular Compounds • As opposed to ionic compounds molecular compounds are not as straight forward to figure out as they can combine in several different ways

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  12. VII. Formula Mass and Moles of Compounds • The average mass of a molecule of a compound is its molecular mass

  13. A. Molar Mass of a Compound and Conversion • Molar mass of a compound is the mass in grams of 1 mole of molecules

  14. Example • If I have 72.5 grams of C3H8O how many molecules of C3H8O is this? • How many carbon atoms are in that many molecules?

  15. VIII. Composition of Compounds • A chemical formula can also give additional information. • The formula along with knowing the molecular weight of the elements can tell us about how much of an element is in a compound

  16. Example • Acetic acid which is CH3COOH, is an active ingredient in vinegar. What is the mass percent of the C, H, and O in acetic acid.

  17. C. Conversion Factors from Chemical Formulas • Chemical formulas contain within them relationships between atoms and molecules. • Given 50.0 grams of CH3COOH how many grams of carbon in the molecule?

  18. IX. Determining Chemical Formulas • We just calculated the mass percent of acetic acid because we knew the formula. But what if we determined the formula from the mass percent?

  19. Example • Given the experimentally determined mass percents below what is the chemical formula? • K = 24.75% • Mn = 34.77% • O = 40.51%

  20. A. Empirical to Molecular Formulas • A molecular formula is just a whole number multiple of the empirical formula • Example: Acetylene is the gas used in welding. It is 92.26% carbon and 7.74% hydrogen. The molecular weight is 26.06g/mole. What is the empirical and molecular formula?

  21. X. Balancing Chemical Equations • Chemical reaction is a process in which one or more substances are converted to different ones.

  22. A. Balancing • Write a skeletal equation by writing formulas of reactant and product • Balance atoms that occur in more complex molecules • Balance atoms that occur as free elements • Check both sides for the same number of atoms

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