UNIT 4: Formulas and Equations (Review Book Topic 2)

How can we distinguish between quantitative and qualitative information?What are the different types of formulas?How can we know that elements form a compound and in what proportions?How can we write formulas?How can we name compounds?What are the different parts of a chemical equation?What are the differences between endothermic and exothermic reactions?How can chemical equations demonstrate the Law of Conservation?What are the different type of chemical reactions?How can we predict products of a chemical reactions?How can we determine an unknown reactant, product, or mass in a chemical equations?

AIM: How can we distinguish between quantitative and qualitative information?

Chemical Symbols: Each element has a unique one-, two-, or three- letter symbol The first letter is always capitalized (Table S,

PT)

Almost all symbols are written without a subscripts as monatomic

Diatomic Molecules: elements that exist in nature as two identical atoms covalently bonded into a diatomic molecule

Br2, I2, N2, Cl2, H2, O2, F2

AIM: How can we distinguish between quantitative and qualitative information?

Chemical Formulas: compounds are composed of elements chemically combined in fixed ratios Formulas use chemical symbols and number to show

both qualitative and quantitative information about a substance

Qualitative: information that relates to things that cannot be counted or measured- What elements are in the compound

Quantitative: information that deals with things that can either be counted or measured The number of atoms of each element in the

compound (subscript or coefficient can give us this info)

AIM: How can we distinguish between quantitative and qualitative information?

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

1. CaCO3

2. Zn3(PO4)2

AIM: What are the different types of formulas

Empirical: simplest ratio Ionic formulas are always empirical formulas

Molecular: actual ratio covalently bonded substances form molecules,

in some cases the empirical represents both empirical and molecular –H2O-

In other cases molecular formula is a multiple of the empirical formula C6H12O6 – six times the empirical CH2O

AIM: How can we know what elements form a compound

and in what proportions? Atoms and compound are electrically neutral

– equal numbers of negative (electrons) and positive (protons)

Ions – can be positive or negative

Ionic charge: indicated by a superscript positive – lost electrons , negative – gained electrons Cl-, Al+3

Polyatomic Ion: group of atoms covalently bonded together, possessing a charge – Table E

AIM: How can we know what elements form a compound

and in what proportions? Forming a compound: many ways – one way:

By attraction of oppositely charged ions

Monatomic or polyatomic ions attract each other in a ratio that produce a neutral compound

Coefficients: written in front of a formula, applies to entire formula, multiple coefficient and subscript to determine the number of each type of element

AIM: How can we know what elements form a compound

and in what proportions? Hydrates

Compounds that contain definite amounts of water molecules

Ex: BaCl2·2H2O – Barium chloride traps 2 water molecules

AIM: How can we write formulas?

Compounds must be electrically neutral

For many elements, the oxidation state is equal to the charge found in the top right corner of each element box

1:1 Na+ & Cl - yields NaCl

Mg2+ & S2- yields MgS

Not 1:1 – Mg2+ & Cl -

Write the charge of one ion as the subscript of the other without the sign (# only)

Thus MgCl2; that is 1 Mg with a 2+ & 2 Cl with 1- each yields (2+) + 2(1-) = 0

AIM: How can we write formulas?

Examples: Write the formulas for the following:

a. Al+3 and Br –

b. Ba+2 and CO3 -2

c. Cu 2+ and CO3 -2

d. Pb +2 and Cl –

e. Pb +4 and CrO4 -2

AIM: How can we name compounds?

Binary Ionic (Metal–positive & Nonmetal–negative)

1st element (metal) – retains its name

2nd element (nonmetal) – change ending to “ide”

Ex: KCl is Potassium chloride

Other Ionic (Contains Polyatomic Ions)

Same as Binary except all polyatomic ions retain their name

Examples:

KNO3 is __________________

NH4Cl is _____________________

NH4NO3 is___________________

Potassium nitrateAmmonium chlorideammonium nitrate

AIM: How can we name compounds?

Examples: Write the names for the following formulas:

a. Mg(SO4)

b. Na(OH)

c. Ca(OH)2

d. Li3(PO4)

e. (NH4)Cl

AIM: How can we name compounds?

Covalent (2 Nonmetals) Need prefixes to tell reader how many of each

Exception – if only one 1st element, don’t use mono

Examples NO is _____________________

N2O4 is _____________________

Stock System (multiple oxidation states) mostly the touchable metals; Iron, Tin, Copper . . .

a Roman numeral proceeding the metal tells the reader the oxidation number

Examples

FeCl2 is _________________

FeCl3 is _________________

Nitrogen monoxideDinitrogen tetroxide

Iron (II) chlorideIron (III) chloride

AIM: What are the different parts of a chemical equation?

Reactant(s) yield Product(s)

Reactant are on the left of the arrow (yield sign) and products are to the right of the arrow

State of matter is indicated by the letter inside the parenthesis

Example: C (s) + O2 (g) → CO2 (g)

Identify the reactants and products in the equation above…….

AIM: What are the differences between endothermic and

exothermic reactions? Endothermic

Heat is required for a reaction to occur, thus, energy is found on the reactant side

Example: H2O (s) + energy → H2O (l)

Exothermic Heat is produced in a reaction, thus energy is found

on the product side

Example: H2O (g) → H2O (l) + energy

AIM: How can chemical equations demonstrate the

Law of Conservation? - BALANCING

The Law of Conservation of Mass & Charge must be upheld

Example:

__ H2 (g) + __ O2 (g) → __ H2O (g)

Remember – It’s coefficient x subscript to find the # of atoms

22 1

AIM: How can chemical equations demonstrate the

Law of Conservation? - BALANCING

Nothing can be created or destroyed – law of conservation of mass Count up the atoms on both side and fill in any missing

elements or compounds

Same thing for missing mass

Practice:

If 103.0g of potassium chlorate are decomposed to form 62.7g of potassium chloride and oxygen gas according to the equation

2KClO3 2KCl + 3O2 how many grams of oxygen are formed?

AIM: What are the different types of

chemical reactions? Synthesis

2 or more reactants form 1 product

A + B → AB

Decomposition 1 reactant breaks down into 2 or more products

AB → A + B

Single Replacement 1 element replaces another

A (element) + BX (compound) → B (element) + AX (compound)

Double Replacement 2 elements/polyatomic ions replace two others

AB (compound) + CD (compound) → AD (compound) + CB (compound)

AIM: How can we predict products of a chemical

reactions? Single Replacement Reactions:

If the individual metal is above the metal that is in the compound a reaction will occur

Double Replacement Reactions:

If a solid is formed (Table F)

If a gas is formed

If a molecular substance such as water is formed

Using TABLE F1. Cross out the first element or compound

2. Look for second element or compound on Table F check to see if it is paired with an exception

3. Determine solubility

Ex)

NH4Cl

MgOH

Soluble

Insoluble

TABLE FAgNO3(aq) + NaCl(aq) AgCl(_____) + NaNO3(____)

s aq

AIM: How can we determine an unknown reactant, product, or mass in a chemical equations?

Nothing can be created or destroyed – law of conservation of mass Count up the atoms on both side and fill in any

missing elements or compounds

Same thing for missing mass