CHEMICAL REACTIONS! Chapter 11

Chemical reactions are occurring around us all the time: 1. Food cooking 2. Fuel being burned in a cars engine 3. Digesting food after a meal...and MANY more 4 Indications a chemical reaction is occurring: 1. Evolution of energy in the form of heat/light (temperature change) 2. Color change 3. Formation of a precipitate 4. Production of a gas

All chemical reactions involve changing substances One or more reactants change into one or more products Chemists use a chemical equation (shorthand notation) to convey as much information as possible

Reactants: chemical compounds or elements that you start with in a chemical reaction Written on the left of the equation Product(s): chemical compounds or elements that you end with (are produced) Written on the right of the equation An arrow separates the reactants from the products Read the arrow as: Yields, reacts to produce, decomposes, or produces Fe + O 2 → Fe 2 O 3

We can show the elements/compounds state of matter using the following symbols: (s) solid (l) liquid (g) gas (vapor) (aq)aqueous solution (substance is dissolved in water) Methane gas + oxygen gas  Carbon dioxide gas + Water vapor CH 4 (g)+ O 2 (g) CO 2 (g) + H 2 O (g) States of Matter

We can indicate if energy was present in the reaction: Reactions that have energy as a reactant are called endothermic reactions: They require energy for the reaction to occur Reactions that have energy as a product are called exothermic reactions Energy happens as a result of the reaction CH 4 (g)+O 2 (g)  CO 2 (g)+H 2 O(g)+energy

Writing Chemical Equations from Word Equations Write the chemical formulas for the reactants to the left of the yields sign (arrow) and the formulas for the products to the right DONT FORGET ABOUT THE 7 DIATOMIC MOLECULES..... Br 2. I 2. N 2. Cl 2. H 2. O 2. F 2

1.Sulfuric Acid (H 2 SO 4 ) 2. Hydrochloric Acid (HCl) 3. Nitric Acid (HNO 3 ) 4. Phosphoric Acid (H 3 PO 4 ) 5. Ammonia (NH 3 ) Need To Be Familiar With:

1. Hydrogen and Oxygen react to produce water 2. Hydrochloric acid reacts with Sodium Hydrogen Carbonate to produce Sodium Chloride, Water, and Carbon Dioxide 3. Aluminum metal reacts with Sulfuric Acid yielding Hydrogen gas and Aluminum Sulfate EXAMPLES:

4.Beryllium Chloride reacts with Silver I Nitrate and yields Beryllium Nitrate and Silver I Chloride powder 5. Sodium and Oxygen react to form Sodium Oxide

PRACTICE… PRACTICE.… PRACTICE…..

BALANCING CHEMICAL REACTIONS

LAW OF CONSERVATION OF MASS During any chemical reaction, the mass of the products is always equal to the mass of the reactants Atoms are neither created nor destroyed in ordinary chemical reactions The same number of atoms of each element must be present on both sides of the equation Add COEFFICIENTS to satisfy this rule NOT subscripts

1Mg(NO 3 ) 2 Mg = N = O = 2Al(NO 3 ) 3 Al = N = O =

How many of each atom are present given the coefficient and compound: 3Ag 3 PO 4 2Mg 3 (PO 4 ) 2 6K 2 SO 4

Reactants (# of atoms) Element Products (# of atoms) Hydrogen and Oxygen react to produce Water

Reactants (# of atoms) Element Products (# of atoms) Iron and Oxygen react to form Iron III Oxide

Calcium chlorate decomposes to form Calcium chloride and Oxygen

Lead II Hydroxide reacts with Hydrochloric Acid to produce Water and Lead II Chloride

Aluminum bromide reacts with Potassium sulfate to produce Potassium bromide and Aluminum sulfate

TIME TO PRACTICE BALANCING!! Complete the balancing chemical equations worksheet

Balance this chemical equation…. ___C 3 H 8 + ___O 2 ___CO 2 + ___H 2 O

Balancing Combustion Reactions Hydrocarbon (C & H compound) + Oxygen yielding Carbon dioxide and Water

1. Determine the # of Hydrogens in the hydrocarbon molecule ODD- Place the coefficient “4” in front of the molecule EVEN- Place the coefficient “2” in front of the molecule 2. Balance both sides of the equations (Left to Right) with the Carbon atoms 3. Balance (Left to Right) the Hydrogen atoms 4. Balance the Oxygen atoms (Right to Left) 5. Reduce the coefficients (If necessary) RULES for BALANCING COMBUSTION REACTIONS:

Ethene (C 2 H 2 ) reacts with Oxygen to produce Carbon dioxide and Water

Pentane (C 5 H 12 ) reacts with Oxygen to produce Carbon dioxide and Water

QUIZ REMINDERS 1.Don’t forget about the 7 diatomic molecules! Make sure to have written the correct chemical equation before beginning to balance Always obey the law of conservation of mass!

DO-NOW For each of the following chemical reactions write the formula equation and balance the equation: 1. Magnesium nitride decomposes into Magnesium and Nitrogen 2. Aluminum sulfate reacts with potassium chloride to produce aluminum chloride and potassium sulfate 3. Magnesium chloride decomposes into magnesium and chlorine 4. Iron (II) sulfate reacts with sodium to produce sodium sulfate and Iron

DO-NOW Calcium Phosphate reacts with Barium Fluoride to produce Calcium fluoride and Barium phosphate Magnesium nitride reacts with Sodium to product sodium nitride and Magnesium 1.CH 4 reacts with Oxygen to produce Carbon dioxide and Water Iron and sulfur react to form Iron II sulfide Potassium chlorate decomposes to form Potassium chloride and Oxygen

1. Synthesis (S) 2. Decomposition (D) 3. Single-Replacement (SR) 4. Double-Replacement (DR) 5. Combustion (C) 5 Types of Chemical Reactions

Types of Chemical Reactions: Starring the Flintstones!

Synthesis A + B AB 2 or more substances react to form one new compound Example: 2Mg + O 2 2MgO

Synthesis + Wilma Fred Fred + Wilma

Decomposition AB A + B A single compound breaks down into 2 or more simpler substances Example: 2BaO 2Ba + O 2

Decomposition +

Single Replacement AB + C AC + B (if C is a nonmetal) AB + C CB + A (if C is a metal) One element replaces another element (based on activity series) Examples: 2Na + MgCl 2 Mg + 2NaCl 2HCl + F 2 2HF + Cl 2

Single Replacement ++ Wilma + FredBetty Betty + Fred Wilma

Double Replacement AB + CD AD + CB The 2 cations in the reactants exchange places to form two new compounds Examples: MgSO 4 + K 2 CO 3 K 2 SO 4 + MgCO 3 MgCl 2 + 2HNO 3 Mg(NO 3 ) 2 + 2HCl

Double Replacement + + Wilma + Fred Barney + Betty

Combustion (burning) A reaction that occurs when a Hydrocarbon reacts with oxygen, producing Carbon dioxide and Water C X H Y + O 2 CO 2 + H 2 O

Burning Money Demonstration! (Combustion)