chemical reactions an expression of the behavior of chemical compounds 1. expressed in a chemical...

Chemical ReactionsAn expression of the behavior of

chemical compounds

1. Expressed in a chemical equation:

Reactant(s) Product(s)(compounds reacting) To Yield (reconstituted

compounds)

Parts of a Chemical Equation

2 Na(s) + 2H2O(l) 2NaOH (aq) + H2(g)

To Yield

Subscripts: # of atoms in compound

Physical State: (s), (l), (g), (aq)

Coefficient: the # of cpd (moles) present. Can be factions, ONLY # that is changed

Reversible reaction: Catalyst: heat, Δ, or compound (FeO2)

Balancing Chemical Equations

ONLY the coefficient can be changed.1. write the compounds (criss-cross) or prefix for molecules.2. Define the type of reaction (activity series and solubility rules)3. Take count of the type and number of elements in the compounds.4. Change of the coefficient ONLY to ensure that the same # and type of each are present on both sides of the arrow.

Word Problem

An aqueous solution of sodium chloride and hydrogen sulfide gas is produced when aqueous sodium sulfide reacts with an excess of hydrochloric acid.

Na2S(aq) + HCl(aq) NaCl(aq) + H2S(g)

Word Problem Sampler

Solid lead is dissolved in aqueous sulfuric acid to precipitate lead (III) sulfate and hydrogen gas is evolved.

Pb(s) + H2SO4(aq) Pb2(SO4)3(s) + H 2(g)

Type of Reactions

1. Synthesis Reaction

2. Decomposition Reaction

3. Single Replacement

4. Double Replacement

5. Combustion Reaction.

Synthesis Reaction

The reaction of two or more reaction to produce a single produce.

a. Form:

A2 + 2CB 2ACB

Sulfur dioxide and water react to produce sulfurous acid

SO2 + H2O H2SO3

Decomposition Reaction

A reaction where one or more reactants breakdown into several simpler forms.

a. Form:

AB2 A + 2B

b. Requires energy to breakdown!

Ammonia breaks down to nitrogen gas and hydrogen gas

2NH3 N2 + 3H2

Single Replacement

• A reaction where the metals (or non-metal) trade places.

• a. Form: AB + C CB + A

• b. Depends directly of the activity of the metal.

Activity Series

• Back of periodic table:

• **The more active the metal (or non-metal), the more likely it is to replace the less active metal (or non-metal).

• **All metals will replace Gold according to the list.

• **Lithium will replace all metals.

• **Fluorine is the most active non-metal.

Sample: Single Replacement

• Sodium plus copper (II) chloride yields sodium chloride and copper metal.

2Na + CuCl2

• Magnesium metal reacts with potassium hydroxide to yield

Mg + KOH

Double Replacement

• a reaction where the metals or non-metals trade positions. (like replaces like).

Form:

AB + CD AD + CB

A precipitate can be formed as one of the produces often.

Sample: Double Replacement

Silver (I) nitrate plus sodium chloride to yield sodium nitrate and silver (I) chloride.

**Balance the charge then balance the equation**

AgNO3 + NaCl

AgNO3 + NaCl NaNO3 + AgCl

Solubility

Ionic compounds ability to dissolve in water.

Solubility Rule:

Note the Periodic Reference Page

Ba(NO3)2

Pb2(SO4)3

C2H4

AgCl2CaCO3

Combustion Reaction

The burning of hydrocarbons in the presents of oxygen and energy.

– Form: Hydrocarbon gas + oxygen carbon dioxide and water. (a complete burn).

CH4 + O2 CO2 + H2O

(a complete burn)

Or

CH4 + O2 CO + H2O

(a dirty burn)

Net Ionic EquationsSpectator Ions: Occurs when reactant

compounds dissolve into solution and ions remain in solution.

– Pay attention to the physical state. (s) indicates that it has NOT ionized (broken down)

– Pay attention to the solubility rules on the periodic table.

– The ions that are on both sides of the equation are called spectator ions and cancel.

– The ions that remain form a net ionic equation.

Sample: Net Ionic Equation

Pb(ClO4)2 (aq) + NaI(aq) PbI2(s) + NaClO4(aq)

Chemical Equation

2Na (s) + 2H2O (l) 2NaOH (aq) + H2(g)

reactants To Yield Products

(s) : solids (l) : liquid (aq): aqueous (g): gas

Coefficient: Big number in front. # of compounds present (# of moles). ONLY number that can change.

Subscript: # of atoms present in the compound

Reversible; Catalyst

Chemical Reaction

An expression of the behavior of chemical compounds

Expressed in a chemical equation:

To yield

Reactant(s) Product(s)

(stuff reacting) (reforming of stuff)

****Energy is required to break or form****

Balancing Chemical EquationsSame number and type of each element

on both sides of the . *Same by changing the coefficient ONLY.*Coefficient in front of cpd ONLY.*Once the charges of a cpd are balanced, NEVER change a subscript!

Review:Writing formula units and molecular formulaCriss-cross to balance charge