Chemical Reactions Chemical rxns occur when atoms are: Separate d As reactants turn into products, what happens to bon holding atoms together ? Old Bon are broken & new Bon are formed Chemical rxn or rear joined ranged ds

Atoms of 1 element never change into other elements in chemical rxn’s (only Nuclear rxns). Why? Atoms - neither created nor destroyed just rearranged in chemical rxns.

 Reactants Arrow, which means: Yields, Reacts to produce, To produce Products What symbol separates the reactants from the products? _____________ Reactant 1 + Reactant 2  Product 1 + Product 2 “Reacts with” to separate 2 reactants “and” is used to separate 2 products Reactants, products Left side is called?Rt. side is called?

II. Writing Chemical Equations A. Chemical equation: describes reactants & products Chemical equations - described 2ways: Written Words Skeletal Equation Writing chemical eq

Rules for writing chemical eq. 1. Include physical states Solid (s), Liquid ( l ), Gas (g), Aqueous (aq) 2. Some elements ONLY appear as diatomics H2 O2 F2H2 O2 F2 rules 3. Some rxns require a catalyst. Catalyst speeds up rxn - not part of product Aqueous means dissolved in water Br 2 I 2 N 2 Cl 2

4. the catalyst - written above or below . KI MoS 2 rules 5. If heat is a catalyst, use a above What happens if both heat & a chemical are catalysts?

A. Written Words Ex 1: Fe (s) + O 2 (g)  Fe 2 O 3 (s), interpret Solid iron to producesolid reacts withoxygen gas iron (III) oxide. Written words, ex 1 Why is oxygen in the example written as O 2 ?

Written Words Example 2: KOH (aq) + H 2 SO 4 (aq)  H 2 O ( l ) + K 2 SO 4 (aq) Aqueous potassium hydroxide to yieldwater reacts with aqueous sulfuric acid and Written words, ex 2 aqueous potassium sulfate.

C. Skeletal Equation What is a skeletal equation? MnO 2 H 2 O (g)H 2 O 2 (aq) + skel eq, ex written as symbols O 2 (g) Ex 1: Manganese (IV) oxide catalyzes the decomposition of aqueous hydrogen peroxide into water vapor and oxygen gas.

Skeletal Equation Ex 2: Solid sodium reacts with water to produce aqueous sodium hydroxide and hydrogen gas. Na (s)  NaOH (aq) + H 2 O( l ) + skel eq, ex written as symbols H 2 (g) Why is hydrogen gas written as H 2 ?

Skeletal Equation Ex 3: Solid sodium hydrogen carbonate reacts with a solution of hydrochloric acid to produce aqueous sodium chloride, water and carbon dioxide gas. NaHCO 3 (s)  NaCl (aq) +HCl(aq) + skel eq, ex written as symbols H2O (l) H2O (l) + CO 2 (g)