Chapter 6 Chemical Reactions and Equations

What are Diatoms? 7 gases must exist as diatoms (two atoms) This means those atoms will NEVER be found alone. They are H 2 O 2 F 2 I 2 N 2 Br 2 Cl 2 ◦ Also known as the HOFINBrCl Twins!

How Do we write a chemical formula? We use what was earned in chapter 5 to translate a word into a chemical formula Copper II Chloride becomes CuCl 2 Dinitrogen Monoxide becomes N 2 O

Example 1 Write the following statement into a chemical formula: Mercury II Oxide decomposes into Merucury and Oxygen

Example 2 Write the following statement into a chemical formula: Aluminum is dropped into a beaker of hydrochloric acid (HCl). The reaction yields Aluminum Chloride and Hydrogen Gas.

Chemical Formulas 2AgNO 3 (aq) + Cu(s) --> Cu(NO 3 ) 2 (aq) + 2Ag(aq) What do all of the things in parentheses mean?

Symbols in Chemical Reactions (s) (l) (g) (aq) Solid Liquid Gas Aqueous (dissolves in water)

Products and Reactants Products are After the Arrow Reactants are Before the arrow They MUST Equal each other ◦ Reactants -- > Products

Is this Balanced? H 2 + O 2 --> H 2 O 

Balance the equation CS 2 + Cl 2 --> CCl 4 + S 2 Cl

Balance: Sodium + Water --> Sodium Hydroxide + Hydrogen Na + H 2 O --> NaOH + H

Combination Two elements combine to make a single compound A + B  AB Magnesium Oxide ◦ Mg + O 2  MgO

Combination Two elements combine to make a single compound A + B  AB Magnesium Oxide ◦ 2Mg + O 2  2MgO

Decomposition One compound forms two elements AB  A + B Mercury Oxide ◦ HgO(g)  Hg(l) + O 2 (g)

Decomposition One compound forms two elements AB  A + B Mercury Oxide ◦ 2HgO(g)  2Hg(l) + O 2 (g)

Single-Replacement An element replaces another element from a compound in an aqueous solution A + BC  AC + B Aluminum in HCl ◦ Al(s) + HCl(aq)  AlCl 3 (aq) + H 2 (g)

Single-Replacement An element replaces another element from a compound in an aqueous solution A + BC  AC + B Aluminum in HCl ◦ 2Al(s) + 6HCl(aq)  2AlCl 3 (aq) + 3H 2 (g)

Double-Replacement Two ionic compounds switch cations AB + CD  AD + CB Potassium Carbonate and Barium Chloride ◦ K 2 CO 3 (aq) + BaCl 2 (aq)  KCl(aq) + BaCO 3 (s)

Double-Replacement Two ionic compounds switch cations AB + CD  AD + BC Potassium Carbonate and Barium Chloride ◦ K 2 CO 3 (aq) + BaCl 2 (aq)  2KCl(aq) + BaCO 3 (s)

Combustion A fuel and oxygen always give CO 2, H 2 0, and HEAT C x H y + (x + y/4)O 2  xCO 2 + (y/2)H 2 O + HEAT Methane Burning ◦ CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O(g) + Heat

Combustion A fuel and oxygen always give CO 2, H 2 0, and HEAT C x H y + (x + y/4)O 2  xCO 2 + (y/2)H 2 O + HEAT Metane Burning ◦ CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(g) + Heat

Reaction Rates All reaction occur at a certain rate of time Four factors can affect how fast or slow a reaction can go

1. Temperature Usually, increasing the temperature increases the reaction rate. Increases the kinetic energy of particles when they collide

2. Concentration (Molarity) More particles reacting means more of a chance for a reaction to occur A higher concentration means a higher reaction rate

3. Particle Size The smaller the particle, the higher the surface area. Higher surface area means something has a better chance to react.

4. Catalyst The addition of a catalyst increases a reaction by lowering the activation energy without using up the catalyst

Activation Energy is the energy needed in order for a reaction to occur