Balancing Chemical Equations West Valley High School General Chemistry Mr. Mata

BALANCING EQUATIONS Law of Conservation of Mass applies to chemical reactions. Discovered by Antoine Lavosier. “Matter is neither created nor destroyed in a chemical reaction”.

An Unbalanced Equation H2 + O2 H2O Why is this equation unbalanced? Answer: There are 2 atoms of O in the reactant, but only 1 in the product.

How to Balance An equation is balanced by adding coefficients. Trial & error procedure. Goal: equal numbers of atoms of each element appear on both sides of the arrow.

REMEMBER: The coefficient (number in front of a chemical formula) multiplied by the subscript gives the total number of atoms.

EXAMPLE 2 H2 means there are 2 x 2 atoms of hydrogen for a total of 4 hydrogen atoms. 2H2O means there are 4 atoms of hydrogen and 2 (2 x 1) atoms of oxygen.

SO LETS BALANCE H2 + O2 H2O The H’s are balanced but the O’s are not. Put a “2” in front of the H2O.

NOW IT LOOKS LIKE THIS H2 + O2 2H2O But now there is a new problem! There are now 4 H on the right! Let’s fix it!!!

HERE’S HOW H2 + O2 2H2O Put a 2 in front of the H2 2H2 + O2 2H2O

IS IT BALANCED? 2H2 + O2 2H2O CONGRATULATIONS, IT’S BALANCED!!! REACTANT ATOMS 4 H 2 O PRODUCT ATOMS 4 H 2 O CONGRATULATIONS, IT’S BALANCED!!!

WARNING! NEVER CHANGE A SUBSCRIPT! (Because that changes the formula of the compound!) NEVER PUT COEFFICIENTS IN THE MIDDLE OF A FORMULA!

TRY THIS ONE __ H2 + __ Cl2 __ HCl H2 + Cl2 2HCl What type of chemical reaction is this? Answer: composition or synthesis

TRY THIS ONE: __Zn + __HCl __ZnCl2 + __H2 Zn + 2HCl ZnCl2 + H2 What type of chemical reaction is this? Answer: single replacement

TRY THIS ONE: __KClO3 __KCl + __O2 2KClO3 2KCl + 3O2 What type of chemical reaction is this? Answer: decomposition

TRY THIS ONE: What type of chemical reaction is this? _H2SO4 + _Al(NO3)3 _HNO3 + _Al2(SO4)3 3H2SO4 + 2Al(NO3)3 6HNO3 + Al2(SO4)3 What type of chemical reaction is this? Answer: double replacement

Chapter 8 SUTW Prompt Describe the method for balancing a chemical equation using proper coefficients. 1 RDF + 3 examples (Hint: steps) in pink. Complete a 6 -8 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink. Due Date: November 7th, 2017 (start of class).