Chemical Reactions

Chemical rxns occur when atoms are:

Separated

As reactants turn into products, what happens to

bon holding atoms together ?Old Bon are broken &

new Bon are formed

Chemical rxnChemical 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, productsReactants, 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 eqWriting 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 F2

rulesrules

3. Some rxns require a catalyst.

Catalyst speeds up rxn - not part of product

Aqueous means dissolved in water

Br2 I2 N2 Cl2

4. the catalyst - written above or below .

KI

MoS2

rulesrules

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) + O2 (g) Fe2O3 (s), interpret

Solid iron

to producesolid

reacts withoxygen gas

iron (III) oxide.

Written words, ex 1Written words, ex 1

Why is oxygen in the example

written as O2?

Written Words

Example 2: KOH (aq) + H2SO4 (aq) H2O (l) + K2SO4 (aq)

Aqueous potassium hydroxide to yield water

reacts with

aqueous sulfuric acid

and

Written words, ex 2Written words, ex 2

aqueous potassium sulfate.

C. Skeletal Equation

What is a skeletal equation?

MnO2 H2O (g)H2O2 (aq) +

skel eq, ex written as symbolsskel eq, ex written as symbols

O2(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) +H2O(l) +

skel eq, ex written as symbolsskel eq, ex written as symbols

H2(g)

Why is hydrogen gas written as

H2?

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.

NaHCO3(s) NaCl (aq) +HCl(aq) +

skel eq, ex written as symbolsskel eq, ex written as symbols

H2O (l) + CO2(g)