8.1 Describing Chemical Reactions

• Chemical Reaction – the process by which one or more __________ are changed into one or more _________ substances

• Follows the law of ________ of mass• Chemical equation – represents, with _______ and formulas, the __________ and relative molar amounts of the _________ and products in a ________ reaction

Evolution of ______ as heat or light

Production of a ___Formation of ________________ change

• The equation must represent _____ facts

• The equation must contain correct ________ for the _________ and the _________

• The law of conservation of ____ must be satisfied

• Coefficient – a small ______ number that appears in _____ of a formula in a chemical ________–Placed in front to _______ an equation

• Word Equation – an equation in which the _________ and products in a ________ reaction are represented by _____

Does not give _______Methane plus oxygen yields carbon dioxide plus water.

Remember ________ molecules.CH4 + O2 CO2 + H2OFormula equation – __________ reactants & products of a chem rxn by their _______ & ________

Use _______ to indicate ______.CH4(g) + O2(g) CO2(g) + H2O(g)

Other symbols on page ___ of book

Also _____ to follow the ___ of ____________ of mass

Add ___________ to _______ eqn.

C2H6 (g) C2H4 (g) + H2 (g)

Physical Catalyst State

ProductsReactants

800 K

Cr2O3

Reversible reaction – a chemical ________ in which the products __-_____ the original reactants.

Catalyst – ______ up a reaction _______ being used up ______ the reaction.

The coefficients indicate ________ not ________ amts.

The relative ______ can be determined by the rxn’s ___________.

The _______ rxn has the same relative _______ of substances as the _______ rxn.

1. Write the unbalanced formula eqn.

2. Count the # of each element3. Insert coefficients for atoms4. Check to make sure both

sides are the same.

1. Delay balancing elements (like H and O) that occur in several reactants or products.

2. If the same polyatomic ions appear on both sides of the equation, treat them as single units, like monatomic ions.

3. After considering 1&2, balance elements left to right.

4. Remember, balancing 1 element may unbalance others.

5. For ionic equations, be sure charges are balanced.

Ammonia plus oxygen yields nitrogen monoxide plus water plus heat.

_____ equationsNeed to make sure ionic _______ are balanced

HCl + H2O Cl- + H3O+

Write the ____ and _______ equations for the chemical reaction that occurs when _____ sodium oxide is _____ to water at room temp and _____ sodium hydroxide (dissolved in the water). Include _______ for physical states & _______ the eqn

Try balancing the following equations…

__Li + __AlCl3 __LiCl + __Al__C + __SO2 __CS2 + __CO__C3H8 + __O2 __CO2 + __H2O__Al(OH)3 + __HBr __AlBr3 + __H2O

__Rb + __S8 __Rb2S__NH3 + __O2 __N2 + __H2O__C6H12O6 + __O2 __CO2 + __H2O__C3H8O + __O2 __CO2 + __H2O