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Chapter 10 – Introduction to Equations Writing and Balancing Equations Section 10.1.

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Presentation on theme: "Chapter 10 – Introduction to Equations Writing and Balancing Equations Section 10.1."— Presentation transcript:

1 Chapter 10 – Introduction to Equations Writing and Balancing Equations Section 10.1

2 Chemical Reactions One or more substances are rearranged to form different substances One or more substances are rearranged to form different substances C 8 H 18 + O 2 -> CO 2 + H 2 O + ENERGY LOOK, IT’S A HYDROCARBON!!!!! The products are carbon dioxide and water! LOOK, IT’S A HYDROCARBON!!!!! The products are carbon dioxide and water!

3 Indicators of Chemical Reactions Animation of Experiment (GIF Format, 321 k) Animation of Experiment (GIF Format, 321 k) Temperature Change Color Change Odor Production of Gas Bubbles Production of a Precipitate

4 Representing Chemical Reactions Statements called equations are used to describe what happens during a chemical reaction Reactants are the starting substances found on the left side of the equation Products are the substances formed during a reaction SymbolMeaning + Separates two or more reactants or products -> Separates reactants from products (s) Solid state (l) Liquid state (g) Gaseous state (aq) Water solution

5 Word Equations and Skeleton Equations Word Equations -Statements that indicate the reactants and products in a rxn -Statements that indicate the reactants and products in a rxn -Describe chemical reactions -Describe chemical reactions -Lack important information -Lack important information Iron (s) + chlorine (g) -> iron (III) chloride (s) Skeleton Equations -Uses chemical formulas to identify reactants and products Fe (s) + Cl 2 (g) -> FeCl 3 (s)

6 Practice Problems Write skeleton equations for the following word equations: 1. hydrogen (g) + bromine (g) -> hydrogen bromide (g) H 2 (g) + Br 2 (g) -> HBr (g) 2. carbon monoxide (g) + oxygen (g) -> carbon dioxide (g) CO (g) + O 2 (g) -> CO 2 (g) 3. potassium chlorate (s) -> potassium chloride (s) + oxygen (g) KClO 3 (l) -> KCl (s) + O 2 (g)

7 Balancing Equations Chemical Equations also must obey the Law of Conservation of Mass. The number of atoms that are used in the reactants must equal the number of atoms found in the products. Matter can neither be created nor destroyed. A chemical equation that follows the law of conservation of mass is called a balanced chemical equation. Chemical Equations also must obey the Law of Conservation of Mass. The number of atoms that are used in the reactants must equal the number of atoms found in the products. Matter can neither be created nor destroyed. A chemical equation that follows the law of conservation of mass is called a balanced chemical equation. A Chemical Equation H 2 + O 2 -> H 2 0 A Balanced Chemical Equation Coefficient… -> 2H 2 + O 2 -> 2H 2 O

8 Balancing Chemical Equations There is a procedure for balancing chemical equations: There is a procedure for balancing chemical equations: 1. Write the equation (remember your diatomic molecules) 2. Count the atoms of each element 3. Add or adjust the coefficients (subscripts cannot be changed) 4. Reduce coefficients to lowest possible terms 5. Check your work Hydrogen + Chlorine Yields Hydrochloric Acid H 2 + Cl 2 -> HCl

9 Balancing Equations Practice Al + O 2 -> Al 2 O 4Al + O 2 -> 2Al 2 O C 3 H 8 + O 2 -> CO 2 + H 2 O C 3 H 8 + 5O 2 -> 3CO 2 + 4H 2 O KNO 3 -> KNO 2 + O 2 2KNO 3 -> 2KNO 2 + 2O 2 O 2 + CS 2 -> CO 2 + SO 2 3O 2 + CS 2 -> CO 2 + 2SO 2


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