Unit 4: Formulas Unit 4: Formulas and Equations and Equations

(If we ever get Review Books it will be (If we ever get Review Books it will be Chapter 2)Chapter 2)

Lesson 1: What Formulas Can Tell Us

• AIM: How can we distinguish between qualitative and quantitative information? What do these words look/sound like?

• Quantitative

• Qualitative

• Chemical Symbols: Each element has a unique one-, two-, or three-letter symbol

• The first letter is always capitalized (Periodic Table and Table S)

• A subscript is a small number sometimes written after a chemical symbol. It tells how many of each atom are present.

• Almost all symbols are written without a subscript and are monatomic (only 1 atom)

• Mn, S, Co, Na, V

Page 1

Symbols with Subscripts

• Diatomic Molecules: elements that exist in nature as two identical atoms covalently bonded together

• Br2, I2, N2, Cl2, H2, O2, F2

Page 1

Parentheses with Subscripts

• If a subscript is written after symbols in parentheses, there are that many of everything in the parentheses

• How many of each type of atom?

Ca(OH)2 Zn(NO3)2

Ca = O = Zn = N =

H = O =

Page 1

Coefficients

• Coefficient: number written in front of a formula, applies to the entire formula

• multiply coefficient and subscript to find number of each type of element

• 2 NH4 : N = H =

• 3 C2H6 : C = H =

Page 1

6 KOH 4 O2

• Chemical Formulas: compounds are composed of elements chemically combined in fixed ratios

• Formulas use chemical symbols and numbers to show both qualitative and quantitative information about a substance

• Qualitative: information cannot be counted or measured (a QUALITY)

• Tell what elements are in the compound

• Quantitative: information that can be counted or measured (a QUANTITY)

• Tells number of atoms of each element in the compound (subscript and coefficient can give us this info)

Page 1

2 CH4NaCl C6H12O6

Homework• Finish both sides of worksheet

• Look through notes and study vocabulary from today

• chemical symbols

• subscripts

• coefficients

• monatomic and diatomic molecules

• qualitative and quantitative information

Do Now, on top of Page 2• Take out your Reference Tables and homework

• Determine the qualitative and quantitative information in the following examples:

CaCO3 Zn3(PO4)2

Qualitative: Qualitative:

Quantitative: Quantitative:

Lesson 2: Types of Formulas

all can be reduced to

AIM: What are the different types of formulas?

• Molecular formula: shows the actual ratio of atoms• covalently bonded substances form molecules

• C6H12O6 H2O2

• Empirical: simplest ratio

• CH2O HO

C2H8 NH4

Page 2

divide by 6 divide by 2

• Sometimes a molecular formula is a multiple (larger version) of the simplified empirical formula

• molecular C6H12O6 is 6 times bigger than empirical CH2O

• Sometimes a molecular formula is also an empirical formula

• Water, H2O : can’t be simplified further

• Ionic formulas are always empirical formulas

• Empirical formulas show “related” or similar molecules with the same ratio of atoms write this part in

Page 2

• Is it a molecular or empirical formula? If molecular, rewrite it as an empirical.

• Hydrates: compounds that contain definite amounts of built-in water molecules• Ex: BaCl2 2 H2O• Barium chloride traps 2 water

molecules

Hydrates