1. CHM 108 SUROVIEC FALL 2015 Molecules, Compounds and Chemical Equations

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 2

3. 3

4. II. Chemical Bonds Hold atoms together and are a result of interactions of the electrons of the atoms 2 main types of bonds 4

5. 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 5

6. 03_01.JPG 6

7. B. Covalent Bonds Nonmetal to nonmetal and the electrons are shared 7

8. III. Chemical Formulas A. Chemical Formulas: indicate the elements present with the relative number of atoms or ions of each. 1. Empirical Formula: gives the relative number of atoms of each element in a molecule 2. Molecular Formula: gives actual number of atoms of each element in a molecule 3. Structural Formula: uses lines to show bonds 8

9. IV. Atomic Level View 1. Atomic elements are those that exist in nature using single atoms of an element 2. 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

10. 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

11. 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 11

12. 03_08-05UN.JPG

13. VII. Formula Mass and Moles of Compounds The average mass of a molecule of a compound is its molecular mass 13

14. A. Molar Mass of a Compound and Conversion Molar mass of a compound is the mass in grams of 1 mole of molecules 14

15. Example 15 1. If I have 72.5 grams of C 3 H 8 O how many molecules of C 3 H 8 O is this? 2. How many carbon atoms are in that many molecules?

16. VIII. Composition of Compounds 16 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

17. Example 17 Acetic acid which is CH 3 COOH, is an active ingredient in vinegar. What is the mass percent of the C, H, and O in acetic acid.

18. C. Conversion Factors from Chemical Formulas 18 Chemical formulas contain within them relationships between atoms and molecules. Given 50.0 grams of CH 3 COOH how many grams of carbon in the molecule?

19. IX. Determining Chemical Formulas 19 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?

20. Example 20 Given the experimentally determined mass percents below what is the chemical formula? K = 24.75% Mn = 34.77% O = 40.51%

21. A. Empirical to Molecular Formulas 21 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?

22. X. Balancing Chemical Equations 22 Chemical reaction is a process in which one or more substances are converted to different ones.

23. A. Balancing 23 1. Write a skeletal equation by writing formulas of reactant and product 2. Balance atoms that occur in more complex molecules 3. Balance atoms that occur as free elements 4. Check both sides for the same number of atoms