Chapter 10 Chemical Equations l A chemical reaction

l A chemical reaction is a reaction in which at least one new substance

l A chemical equation is a shorthand method of writing a chemical reaction using

Symbols Used in Equations (g) – gas l (cr) – crystalline solid l (l)

Law of Conservation of Mass l In an ordinary chemical reaction, mass can neither

Balancing Chemical Equations l 1. Count the number of atoms of each element on

Practice Website l www. chem. vt. edu/RVGS/ACT/notes/script s/bal_eq 1. html

Balancing NO-NO’s l Coefficients can only be added BEFORE a chemical symbol or formula.

Signs a Chemical Reaction Has Occurred: Color change l Liberation of a gas l

5 Major Types of Chemical Reactions 1. Synthesis Reaction – 2 or more reactants

Rust is the product of a synthesis reaction.

2. Decomposition Reaction – the breakdown of one reactant into its components. Example -

3. Single Replacement Reaction – one element replaces another in a compound. Example -

4. Double Replacement Reaction – the positive and negative ions of two reactants exchange

Many times a precipitate is the result of a double replacement reaction.

5. Combustion – the burning of an organic compound in oxygen to form CO

Welding is an example of a combustion reaction.

Practice – Classifying Reactions 1. 2. 3. 4. Cl 2 + 2 KBr KCl

Activote Quiz Ca. O + H 2 O Ca(OH)2 This equation is an example

Writing Chemical Equations 7 Diatomic elements Chlorine Fluorine Iodine Bromine Oxygen Nitrogen Hydrogen

Common Acids Sulfuric acid l Nitric acid l Carbonic acid l Hydrochloric acid l

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Chapter 10 Chemical Equations

l A chemical reaction is a reaction in which at least one new substance is formed. l Example – Hydrogen and oxygen react to form water.

l A chemical equation is a shorthand method of writing a chemical reaction using chemical symbols and formulas. l Example – H 2 + O 2 H 2 O

Symbols Used in Equations (g) – gas l (cr) – crystalline solid l (l) – liquid l (aq) – aqueous solution l

Law of Conservation of Mass l In an ordinary chemical reaction, mass can neither be created nor destroyed. l Mass of products must equal the mass of the reactants.

Balancing Chemical Equations l 1. Count the number of atoms of each element on both sides of the equation. l 2. Use coefficients to balance the equation. l 3. Always use the lowest possible ratio of coefficients to balance.

Examples

Practice Website l www. chem. vt. edu/RVGS/ACT/notes/script s/bal_eq 1. html

Balancing NO-NO’s l Coefficients can only be added BEFORE a chemical symbol or formula. l NEVER change a subscript to balance an equation.

Signs a Chemical Reaction Has Occurred: Color change l Liberation of a gas l Energy change l Formation of a precipitate l Change in odor l

5 Major Types of Chemical Reactions 1. Synthesis Reaction – 2 or more reactants combine to form one product. Example-

Rust is the product of a synthesis reaction.

2. Decomposition Reaction – the breakdown of one reactant into its components. Example -

3. Single Replacement Reaction – one element replaces another in a compound. Example -

4. Double Replacement Reaction – the positive and negative ions of two reactants exchange places. Example-

Many times a precipitate is the result of a double replacement reaction.

5. Combustion – the burning of an organic compound in oxygen to form CO 2 and H 2 O and energy. Example -

Welding is an example of a combustion reaction.

Practice – Classifying Reactions 1. 2. 3. 4. Cl 2 + 2 KBr KCl + Br 2 2 Ag 2 O 4 Ag + O 2 2 Na + Cl 2 2 Na. Cl Pb. Cl 2 + Li 2 SO 4 Pb. SO 4 + 2 Li. Cl

Activote Quiz Ca. O + H 2 O Ca(OH)2 This equation is an example of which type of chemical reaction: a. Decomposition b. Synthesis c. Combustion d. Single Replacement

LAB – Chemical Reactions