Balancing chemical equations

Balancing chemical equations:

Important to remember that we only WRITE COEFFICIENT NUMBERS; whole numbers written in front of an alphabet [ Also known as MOLES] to balance a chemical equation.

e.g. A is the same as 1A that is   1 x A = A, therefore A has coefficient of 1 ,  2A coefficient of 2 ,     3B has coefficient of 3.

WE CANNOT write SUBSCRIPTS OR SUPERSCRIPTS to balance a chemical equation.

• A ^____> A₂
• We cannot write   A₂ ^_____> A₂       instead we write 2A ^______> A_{2    ………[balanced]}

 Let balance this; A + B ^_______> A₂B₅    

 List the items or elements and count on each side of the equation.

    

	A	B
Left side	1	1
Right side	2	5

Now multiply through by using coefficients to make left side equal to the right side of the equation.

                                               

	A	B
Left side	1x2	1x5
Right side	2	5

Re-write equation.

2A + 5B ^______>  A₂B₅    …………[balanced equation]

 

SPLIT METHOD

An element that appears in two or more different compounds at the same side of an equation must be counted separately for each compound instead of the sum.

E.g. In the illustration below, Element B appearance in two compounds at the left side of this equation below can cause the balancing of the equation to be complicated but it is made easier by splitting the number of B into two (5 and 3) at the left side in the list instead of writing the sum 8.

Let balance this;       A₂B₅ + B₃C₂ ^____> AC₃ + B

List the items or elements and count on each side of the equation.

    

	A	B	C
Left side	2	5+3	2
Right side	1	1	3

Now multiply through by using coefficients to make items on left side equal to the right side

           

	A	B	C
Left side	2	5 + 3x3 (second step) =14	2x3
Right side	1x2 (first step)	1x14 (third step)	3x2

A₂B₅ + 3B₃C₂ ^____> 2AC₃ + 14B ……….[balanced equation]

 

GROUP METHOD

Polyatomic ions appear as group in a compound, but these can be listed as one entity for each compound if they appear the same in both sides of the equation [left (reactant) and right (product) side].

In this illustration, below the polyatomic groups are YZ and CHD. These are counted as single entities since they appear the same on both sides of the equation. This makes it easier to balance the equation given.

E.g. Let’s balance this;        A(YZ)₂ + BCHD ^____> A(CHD)₂ + BYZ ……..[not balanced]

List the items or elements and count on each side.

                             

	A	B	CHD	YZ
Left side	1	1	1	2
Right side	1	1	2	1

Now multiply through by using coefficients to make left side equal to the right side of the equation.

 

	A	B	CHD	YZ
Left side	1	1x 2 (second step)	1x 2	2
Right side	1	1x 2 (first step)	2	1x 2

 

A(YZ)₂ + 2BCHD ^____> A(CHD)₂ + 2BYZ………….[balanced equation]

EXAMPLES

Reaction of nitrogen dioxide with water

Complete combustion of hexene in oxygen gas

Reaction of Sodium hydroxide with sulfuric acid

NaCl + H₂SO₄

The following videos below should give more information on balancing chemical equations.

Basic understanding of Coefficient listing method.

How to solve more difficult problems

VIDEO

BALANCING IONIC EQUATIONS

This is a follow up of balancing equations;

Balance equations without ions are MOLECULAR EQUATIONS.

Ions of elements that form soluble ionic compounds; group 1 and 2 elements, e.g., K⁺, Na⁺, and all group 1 metal compounds etc.

Polyatomic ions that form soluble ionic compounds; e.g. NO₃^–, NH₄⁺, ClO₄^–, ClO₃^–

Ions that form insoluble compounds or precipitates; e.g. OH^–, SO₃^-2, CO₃^-2, S^-2, PO₄^-2-

Presence of any soluble ion makes the whole compound soluble even if an insoluble ion is present.

Only Soluble compounds [aka AQUEOUS= (aq)] can   be separated into constituent ions. Every other state cannot be separated; e.g. Solid (s), liquid (l) or gas (g).

Use COEFFICIENT NUMBERS to show the number of ions or balance equations. E.g. K₃PO₄ is; 3 K⁺ ions in contact with a PO₄^-3 ion. The Al(NO₃)₃  is one AI⁺³ ion in contact with 3 NO₃^– ions.

Spectator ions are the same on both left and right side of equation and cancel out to give overall ionic equation.

You can determine if there is a chemical reaction by checking if anything other than aqueous if formed [that is solid (insoluble) =precipitate(s), liquid(l) or gas(g) is formed.]

Example 1

Write a balanced the ionic reaction between sodium hydroxide and hydrochloric acid to form water.

                           NaOH + HCI ^_______> NaCI + H₂O …  [balanced already]

2. Write the overall balanced ionic equation for reaction below;

Aluminum hydroxide reaction with nitric acid to form aluminum nitrate and water           

Al(OH)₃ + HNO₃ ^_______> AI(NO₃)₃ + H₂O [not balanced]

Ionic equation

Example 3

Write a balanced reaction between lead (ll)nitrate and HCl

Pb(NO₃)₂ + HCl

Reaction between lead(ll)nitrate and HCl forms lead(ll)chloride and nitric acid

Pb(NO₃)₂ + HCl ^________> PbCl₂ + HNO₃   …… [unbalanced equation]

P.S. use the previous above method of (SPLIT AND GROUP) to balance the molecular equation.