1. Chemical Equations Objectives: 1. Explain how a chemical equation describes what happens in a chemical reaction. 2. Explain how a balanced chemical equation illustrates the law of conservation of matter. Key Terms: Chemical equation, Balanced chemical equation, Coefficient

2. Chemical Equations A chemical equation is the shorthand used by chemists to describe a chemical reaction. Just as in math the equation matches the number and type of reactants with the products. Atoms to the left of the arrow Reactants Atoms to the right of the arrow Products ,  yields (forms, produces, makes,...) +separates individual atoms or compounds Coefficientnumber directly before an atom or compound (multiplies the entire substance) Subscript numbernumber within a compound (multiplies what precedes it) Solid(s) Liquid(l) Aqueous(aq) Gas(g)

3. Chemical Equations The types and numbers of atoms in the reactants must match the type and numbers of atoms in the products. – Must follow the Laws of Conservation of Mass, Matter, & Energy When the atoms in the reactants match the products the equation is said to be balanced. – to balance an equation you may only change the coefficient – A chemical equation that is balanced for charge using subscripts but does not have coefficients is called a skeleton equation

4. Balancing Chemical Equations 1.AgNO 3 + H 2 S  Ag 2 S + HNO 3 2. Zn(OH) 2 + H 3 PO 4  Zn 3 (PO 4 ) 2 + H 2 O 3. hydrogen + sulfur yields hydrogen sulfide (hint: Remember your diatomic molecules) 4. iron (III) chloride + calcium hydroxide yields iron (III) hydroxide + calcium chloride

5. Balance the top equations by only changing the coefficients 1. 2AgNO 3 + H 2 S  Ag 2 S + 2HNO 3 2. 3Zn(OH) 2 + 2H 3 PO 4  Zn 3 (PO 4 ) 2 + 6H 2 O 3. H 2 + S  H 2 S 4. 2FeCl 3 + 3Ca(OH) 2  2Fe(OH) 3 + 3CaCl 2 When you count the number and types of atoms on each side of the equation they should match