CHEMICAL EQUATIONS AND REACTIONS
A chemical reaction is __________________________________________________
____________________________________________________________________.
A chemical equation is __________________________________________________
_____________________________________________________________________.
RULES FOR WRITING CHEMICAL EQUATIONS:
1) You must know how the substances react and what new substances they form.
2) You must know the correct formulas of the reactants and products.
3) Every chemical equation must balance. (The Law of Mass Conservation must be
satisfied).
Word Equations: _______________________________________________________.
Formula Equation: _____________________________________________________.
TERMS TO KNOW:
Reactants: ____________________________________________________________.
Products: _____________________________________________________________.

:______________________________________________________________.
+ sign: _____________________________________________________________.
Physical States of the Substances are often indicated:
Gas: _________________________________________________________________.
Liquid: _______________________________________________________________.
Solid: ________________________________________________________________.
Aqueous: _____________________________________________________________.
Other Symbols:

: Heat added
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Pt :

 : ________________________________________________________________
300  C

: _____________________________________________________________
Practice Writing Word and Formula Equations:
1. Calcium reacts with sulfur to produce calcium sulfide.
2. Sodium reacts with fluorine to produce sodium fluoride.
3. Carbon disulfide solid reacts with oxygen gas to produce carbon dioxide gas and
sulfur dioxide gas.
4. Aqueous solutions of potassium chloride and silver nitrate react to produce
aqueous potassium nitrate and solid silver chloride.
5. Ca(OH)2(aq) + H3PO4(aq)
6. Fe(s) + HCl(aq)
7. KNO3(s)
Ca3(PO4)2(s) + H2O(l)
FeCl2 (aq) + H2(g)
KNO2(s) + O2 (g)
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GUIDELINES FOR BALANCING CHEMICAL EQUATIONS
Balancing by Inspection:
According to the Law of Conservation of Matter, mass must be conserved in a chemical
reaction.
Therefore, there must be the same number of atoms or moles of atoms of each element
before and after the reaction. (On each side of the equation).
Balancing by inspection is just a process used to look at the equation & make sure all
elements are balanced on each side of the equation.
Guideline 1:
Write the correct formulas for the reactants and the products, using the correct symbols.
Once you have written a correct formula, DO NOT change it during the balancing
operation. Instead, place numbers called coefficients in front of the formula to obtain a
balanced equation.
Example:
Guideline 2:
Select an element to begin balancing the equation. Usually select the element from the
compound containing the most atoms that is present in the largest number. DO NOT
select an element in a polyatomic ion, DO NOT select H or O.
Example:
Guideline 3:
Next, balance the polyatomic ions that remain the same on both sides of the equation.
Balance these as a single unit. (Sometimes you may have to adjust the coefficient you
used in the previous step).
In this example ____________ remains unchanged.
Example:
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Guideline 4:
Balance the H atoms, then the O atoms. If they appear in the polyatomic ion you
already balanced, DO NOT consider them again.
Example:
Guideline 5:
Check all coefficients to make sure they are WHOLE NUMBERS, in the lowest possible
ratio. If any coefficients are fractions, multiply the equation by the denominator to make
coefficients whole numbers. If not smallest ratio, reduce.
BALANCE BY INSPECTION EXAMPLES:
For each of the following, write the formulas and balance the equation.
1. Solid iron metal & aqueous hydrochloric acid react to produce aqueous iron(II)
chloride and hydrogen gas.
2. Aluminum hydroxide and phosphoric acid react to produce aluminum phosphate
and water.
3. Butane gas (C4H10) and oxygen react when heated to produce carbon dioxide
gas and liquid water.
4. Solid potassium nitrate is heated to produce solid potassium nitrite and oxygen
gas.
5. Hydrochloric acid is added to limestone (calcium carbonate) producing carbon
dioxide gas, water, and calcium chloride.
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More Practice:
Change the following word equations into chemical equations and balance them.
1. Sodium chloride + Lead (II) nitrate
Lead (II) chloride + Sodium nitrate
2. Ferric oxide + Hydrochloric acid
Ferric chloride + Water
3. Sodium hydrogen carbonate + phosphoric acid  Sodium phosphate + Carbon dioxide + Water
4. Calcium iodide + sulfuric acid
Hydrogen Iodide + Calcium sulfate
5. Barium nitrate + Sulfuric acid
Barium sulfate + Nitric acid
6. Iron (II) sulfide + Hydrobromic acid
Hydrosulfuric acid and Iron (II) bromide
7. Sodium hydrogen sulfite + Sulfuric acid
Sodium sulfate + Sulfur dioxide + Water
8. Aluminum sulfate + Sodium hydroxide
Aluminum hydroxide + Sodium sulfate
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