WRITING CHEMICAL EQUATIONS THX.

The 4 steps; 1. Write the reaction down in words. This is often called the word equation 2. Replace each name with the correct symbol or formula. Symbols are used for elements, a formula for a compound 3. Add details about physical state and conditions if known. (s,l,g or aq) 4. Balance the equation (the mass on both sides must be the same)

I. THE MEANING OF A CHEMICAL EQUATION A chemical equation is a chemist’s shorthand expression for describing a chemical change. As an example, - consider what takes place when iron rusts. The equation for this change is: In this expression, the symbols and formulas of the reacting substances, called the reactants, are written on the left side of the arrow and the products of the reaction are written on the right side. The arrow is read as “gives”, “yields”, or “forms”

II. BALANCING A CHEMICAL EQUATION Law of Conservation of Matter. That is, there must be the same number of atoms of each element on the right hand side of the equation as there are on the left hand side. If the number of atoms of each element in the equation above are counted, it is observed that there are 1 atom of Fe and 2 atoms of O on the left side and 2 atoms Fe and 3 atoms of O on the right. A Chemical equation must conform to the..

i. Aluminium + bromine bromide Aluminium

If the number of atoms of each element in the equation above are counted, it is observed that there are 1 atom of Fe and 2 atoms of O on the left side and 2 atoms Fe and 3 atoms of O on the right.

The balancing of the equation is accomplished by introducing the proper number or coefficient before each formula. To balance the number of O atoms, write a 3 in from of the O 2 and a 2 in front of the Fe 2 O 3 : The equation, above, now has 6 atoms of O on each side, but the Fe atoms are not balanced. Since there is 1 atom of Fe on the left and 4 atoms of Fe on the right, the Fe atoms can be balanced by writing a 4 in front of the Fe:

weblink flashlinks isreaction.swf

magnesium + carbon dioxide magnesium oxide + carbon Mg + CO 2 MgO MgO 2 +

magnesium + hydrochloric acid magnesium chloride + hydrogen Mg HCl 2 + HCl MgCl MgCl 2 H2H2

Write these as WORD EQUATIONS first!!