SCN 2D – Balancing Chemical Equations Oct 20, 2008

Lavoisier’s Law of Conservation of mass: total mass of reactants is always equal to the total mass of products

Dalton’s Atomic Theory: 1) All matter is made up of atoms 2) Atoms cannot be created of destroyed 3) Atoms of the same element are identical in mass and size, but are different in mass an size from all other elements 4) Compounds are formed when atoms of different elements combine in fixed ratios

Chemical Equations Word equation: equation written in words Hydrogen + oxygen  water (*label)

Skeleton equation: summarizes a chemical equation using element symbols, but not complete or accurate H 2 +O 2  H 2 O (** BOARD add the total atomic weights of the eq’n **)

Atomic weights of products and reactants aren’t equal, BUT according to Lavoisier’s Law and Dalton’s Atomic Theory, both sides must add up

So…  we use coefficients in front of elements so that the number/type of atoms on the products side equal the number/type of atoms on the reactant side

Balanced chemical equations: have appropriate coefficients so that the reactant elements = the product elements

Turn to pg. 171 in text Let’s work out example H 2 + O 2 = H 2 O

More Examples… 2) Na + H 2 O  NaOH + H 2 3) Cu + AgNO 3  Cu(NO 3 ) 2 + Ag