A chemical reaction is simply a chemical change Atoms rearrange themselves to form

new compounds

Production of a gas (bubbles)Production of a solid (precipitate)Color ChangeProduction of heat/light (energy)Noise (ex: sizzling)

Only the evidence of a NEW substance after chemical analysis is 100% proof of chemical reaction

A systematic way to write a chemical reaction using symbols Shows compounds involved in the

reaction States of matter Changes in energy (endo or exo) Quantifies reaction (ratios between

compounds)

Ex: Hydrogen gas and oxygen gas react together to produce water

Ex:

2H2(g) + O2(g) 2H2O(l)

Reactants Products

“and” (Separates reactants or products)

“Yields” or “Produces”

Cu(s) + 2AgNO3(aq) 2Ag(s) + Cu(NO3)2(aq) ΔH = -484 kJ

States of matter ▪ (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous

Coefficients▪ Tell us the mole ratio between reactants/products.

Enthalpy▪ Tells if the reaction gives off energy (exo) or needs energy

(endo)

At standard conditions, here are the following states of matter:

Metal atoms are solids Ionic Compounds are typically solid

or aqueous (dissolved in water)Nonmetals are gases Bromine/Mercury are liquid

Metals are listed as a single element (i.e. Iron Fe)

Carbon can be listed as C(graphite) or C(diamond)

Remember diatomics (i.e. F2, Cl2, H2) Phosphorus can be P4 and Sulfur can be S8

A species written over the arrow indicates a “helping” substance, though doesn’t affect chemicals involved Ex:

H2O Δ

Six general types of reactions Synthesis/Combination Decomposition Combustion Single Replacement (Displacement) Double Replacement (Displacement) Acid/Base Neutralization

Reaction between two or more substances (reactants) and making ONE PRODUCT (compound)

Form:A + B AB

Example: 2Na + Cl2 2NaCl

Reaction of ONE REACTANT breaking down into its elementary substances

Form:AB A + B

Example:H2O H2 + O2

Carbon-based compound reacting w/ oxygen (burning) “CXY” could be a hydrocarbon or also contain

oxygen Products are ALWAYS CO2 and H2O

Form:CXY + O2 CO2 + H2O

Example:CH4 + 2O2 CO2 + 2H2O

What type of reaction are the following? N2 + H2 NH3

C2H8 + O2 CO2 + H2O H2 + O2 H2O KClO3 KCl + O2

Ag2O Ag + O2

S8 + O2 SO3

CH4 + O2 CO2 + H2O H2O H2O + O2

Chemical reaction where one element replaces another element in a compound “Like” replaces “like” (ex: metals switch) An ELEMENT and a COMPOUND for

REACTANTS Form:

A + BC B + AC Example:

Al + CuCl2 AlCl3 + Cu

A BC

You must look at the Activity Series to determine if a cationic replacement reaction will happen.

Ex:

Zn(s) + HCl(aq) H2 + ZnCl2

Cu(s) + HCl(aq) No Reaction

Chemical reaction where two elements (or polyatomic ions) in different compounds switch places TWO COMPOUNDS for REACTANTS

Form:AB + CD CB + AD

Example: Na2SO4 + AlCl3 Al2(SO4)3 + NaCl

A CDB

Special type of Double ReplacementWhere an Acid (containing H+) and a

Base (containing OH-) react to produce A Salt (ionic compound) and Water (HOH or H2O)

Ex: HCl + NaOH NaCl + HOH (H2O)

Determine the type of reaction. **Predict the products for the starred reactions **Na2S + ZnCl2

Mg(OH)2

**H2 + Cl2

C6H6 + O2

K + Fe(OH)3

F2(aq) + KI(aq) **HF(aq) + NaOH(aq) **C10H8 + O2

H2 + O2 H2O

Law of Conservation of Matter/Mass: Matter (atoms) cannot be created or destroyed

In other words, same # of atoms on both sides

Ex: Balance the above chemical equation

Step 1: List elements on both sidesStep 2: Write down the number of

atoms for all the elementsStep 3: Use coefficients to balance

atoms DO NOT CHANGE THE SUBSCRIPTS!!!!!

Ex: __FeS +__HCl __FeCl2 + __H2S

Here are some tips to balancing some difficult equations Are there any “2:3” ratios? Do those elements

first▪ Ex: AlCl3 + ZnBr2 AlBr3 + ZnCl2

Balance metals first If you have the same polyatomic on both

sides, treat the polyatomic as ONE▪ Ex: Na3PO4 + CaCl2 Ca3(PO4)2 + NaCl

▪ Na2CO3 Na2O + CO2

Try to balance Oxygen and Hydrogen at the end.

Balance carbons first Balance hydrogens second Balance oxygens last If you end up having an odd # of

oxygens on the product side, put a decimal coefficient in front of oxygen on reactant side that will make it balance, THEN DOUBLE EVERY COEFFICIENT to make whole #s Ex: ___C2H6 + ___O2 ___CO2 + ___H2O

__Li3PO4 + __SrCl2 __Sr3(PO4)2 + __LiCl

__Fe2O3 + __H2SO4 __Fe2(SO4)3 + __H2O

__C5H12 + __O2 __CO2 + __H2O

Balance the following equations and state what kind of reaction it is:

_____ N2 + _____ O2 _____ N2O ____KClO3 ____KCl + ____ O2 __ Al(OH)3 + __ H2SO4 __ Al2(SO4)3 + __

H2O

Determining the empirical formula of an organic compound

1) Convert your known quantities of CO2 and H2O into grams of C & H only

2) Determine how many grams of oxygen (if any) are present in the compound as well.

3) Turn your grams of C, H, & O into moles of C, H, & O, respectively.

4) Compare your 3 answers from step 3 and divide ALL 3 answers by the lowest # you get (this is your ratio, and therefore your subscripts)

18.8 g of an unknown organic substance produced 27.6 g of carbon dioxide and 11.3 g of water.

What is the empirical formula?

Used to predict amount of product produced or how much reactants were used

Remember: Coefficients tell us MOLE ratio

N2(g) + 3H2(g) 2NH3(g)

How many moles of ammonia are created when 2 moles of nitrogen are used? 6 moles of hydrogen?

How many moles of nitrogen are needed to make 4 moles of ammonia?

What mass of lithium nitride is produced when 75.0 g of lithium metal react with excess nitrogen?

6Li(s) + N2(g) 2Li3N(s)

What is the mass of O2 necessary to react with 5.71 g Al?

4Al(s) + 3O2(g) 2Al2O3(s)

Given the following equation: 2 KClO3 ---> 2 KCl + 3 O2

How many moles of O2 can be produced by letting 12.00 moles of KClO3 react? (watch sig figs!!!)

Given the following equation: 2 K + Cl2 ---> 2 KCl How many grams of KCl are produced from 2.50 g

of K and excess Cl2 ?

Although we want all reactants to be completely used up, in reality there is usually one reactant that is used up before the other and thus LIMITS the reaction and how much can be produced.

Limiting Reactant: The reactant that is completely consumed (runs out first) Limits the reaction Nothing is left over

Excess Reatant: The reactant left over Not completely consumed

Though every stoichiometry problem is unique, the same general steps are used:

1)Convert given chemical(s) into MOLES2)Use MOLE RATIO to convert from given

chemical to desired chemical*After this step is where you would determine limiting reactant IF it applies to the problem

3)Convert desired chemical into DESIRED UNIT (ex: grams, liters, etc.)

How many moles of NH3 can be produced from the combination of 3.0 moles N2 and 1.5 moles H2?

What mass of water is produced when you react 12.4 g of H2 with 13.5 g of oxygen?

If you have 11.5 L of nitrogen reacting with 16.5 L of hydrogen, what volume of ammonia is produced at STP? (At STP 1 mole of any gas = 22.41 L)

If you have 1.22 g of O2 reacting with 1.05 g of H2, what mass of water will you produce?

When amount of product is calculated using stoichiometry, this is known as theoretical yield What you theoretically SHOULD get

When you perform the experiment in the lab, you typically get less, this is known as actual yield

Actual Yield x 100 = % Yield Theoretical Yield

Ex: Magnesium burns in air. If you burn 6.73 grams of Magnesium: How many grams of product would you

produce? What would be your percent yield if you did

the experiment and got 10.7g of the product?

Suppose you react sulfur dioxide with oxygen to produce sulfur trioxide. If you react 12.4 g of sulfur dioxide with 3.45 g of oxygen, how many grams of sulfur trioxide will you produce?

If you did this lab and yielded 13.4 grams of sulfur trioxide, what is your percent yield?

Group 1A metals tend to be highly reactive toward oxygen, water, and acid. M + H2O MOH + H2

Lithium forms oxides (Li + O2 Li2O) The other alkali metals form oxides or

peroxides (O22- ion) (Na + O2 Na2O2)

K, Rb, and Cs can also form superoxides (containing the superoxide ion O2

-)

Group 2A metals are less reactive

Be doesn’t react with water, Mg reacts slowly to steam, and Ca, Sr & Ba react strongly with cold water to form hydrogen gas and hydroxides Ca + H2O Ca(OH)2 + H2

React w/ oxygen (Be and Mg only at high temps)

React with acids form hydrogen gas

Boron (a metalloid) is unreactive to oxygen and water; all other elements are metals and tend to be reactive

Aluminum will readily form aluminum oxide when exposed to air (oxygen)