Midterm Review

Topic 2 Formulas and Equations

Vocabulary

Chemical Symbols and Formulas

• Chemists have developed a universal language by which they can communicate chemical information and have the information understood by scientists around the world

Diatomic Molecule

• BrINClHOF

Chemical Formulas

• Compounds are composed of combinations of elements chemically combined in definite proportions– Formulas us chemical symbols and numbers to show

both qualitative and quantitative information about a substance

– The chemical formula CO tells the reader that the compound consists of Carbon and Oxygen.

– The chemical formula CO2 tell the reader that the compound consists of 1 carbon and 2 oxygen atoms

Types of Formulas• Empirical Formula– Represents the simplest ratio in which atoms

combine to form a compound• Molecular Formula– Covalently bonded substances form discrete units

called molecules. • In some cases, such as H2O, the chemical formula is

both empirical and molecular• In other cases the molecular formula may be a multiple

of the empirical formula, for example glucose, C6H12O6

Atoms, Compounds, and Ions• Ionic Charge– The charge of an ion is indicated

by the superscript following the symbol of the ion.

– Al+3

• Polyatomic Ions– A polyatomic Ion is a group of

atoms covalently bonded together, possessing a charge• Reference table E

Atoms, Compounds, and Ions

• Forming a Compound– Compounds can be formed in several different

ways• One way is the attraction of oppositely charged ions• Monatomic or polyatomic ions attract each other in a

ration that produces a neutral compound

Atoms, Compounds, and Ions

• Coefficients– The coefficient tells how many units of the

formula are present

Atoms, Compounds, and Ions

• Hydrates– When water from come ionic solution evaporates,

the solute forms a crystal lattice that binds water with in the structure

– CuSO4• 5H2O

Writing Formulas and Naming Compounds

• Equalizing charges– Compounds achieve neutrality by having an equal

number of positive and negative charges. – When sodium ion (Na+1) and a chlorine ion (Cl-1)

combine, they will do so in a 1:1 ratio– If you do not have a 1:1 ratio, they you must cross

down the charges

Writing Formulas and Naming Compounds

• Naming Compounds– Compounds are named according to the types of

elements that form them. • Ionic compounds

– Binary or polyatomic

• Covalent compounds – Binary or stock system

Chemical Reactions and Equations

• Physical Change– A change in state such as ice melting

• Chemical change– The substances produced are quite different form

the starting material

Chemical Reactions and Equations• Chemical Equations

Chemical Reactions and Equations

• Endothermic reaction

• Exothermic reaction

Chemical Reactions and Equations

• Balancing chemical equations– Law of Conservation of Mass

Types of Chemical Reactions

• Synthesis – A+B AB

Types of Chemical Reactions

• Decomposition– AB A + B

Types of Chemical Reactions

• Single Replacement– AB + C AC + B

Types of Chemical Reactions

• Double Replacement– AB + CD AD + CB