The law of conservation of matter states that, in a system that is closed to the transfer of matter, the amount of matter in the system remains constant. Simply put, the amount of matter in the system is conserved. You may have heard this law, but what does it mean to Chemistry students? Per this law, you should always balance a chemical equation so that the amount of matter on the reactant side is equal to that on the product side. This is where Balancing Chemical Equations Worksheets come in handy.
Many students struggle with balancing chemical equations at first because it requires perfect mastery of chemical formulae, reactions symbols, and valences, among other concepts. Fortunately, all you need is practice. Read on to learn more about how to use a worksheet to improve your balancing skills.
What Is a Chemical Equation?
A chemical equation is a relationship between chemical reactants and the products they form during a chemical reaction as represented by their chemical formulae. It contains the reactants (elements reacting with each other), products (elements produced in the reaction), and symbols that represent the relationships (plus signs and arrows). Here is an example of a chemical equation:
2Na + 2HCl –> 2NaCl + H2
From this example, there are two atoms of sodium, hydrogen, and chlorine, each on both sides of the equation. This is a balanced chemical equation representing the reaction between sodium metal and hydrochloric acid (reactants) to produce sodium chloride solution and hydrogen gas (products).
What Is a Balancing Chemical Equations Worksheet?
A balancing chemical equation worksheet is a practice booklet with unsolved and solved chemical equation problems on which students can practice their balancing skills. If all the problems are unsolved, it will usually contain an answer section that students can use to gauge their performance. Generally, chemical equation worksheets can be provided by schools or sourced online.
Balancing Chemical Equations Worksheets
How to Balance a Chemical Equation
In most cases, you will be provided with chemical reactants, and it is up to you to determine the products, write the chemical equation, and balance it. For this guide, we will use hydrogen (H2) and oxygen (O2) as our reactants. The product is water (H2O), and the chemical equation:
H2 + O2 –> H2O
This equation is unbalanced because there are two atoms of oxygen on the product side and only one on the reactant side. We will balance it as follows:
Step 1: List the Elements
Start by identifying the elements in the reactants and those that make up the compound that is the product. From our example, you can list the s follows:
- Reactant elements – H, O
- Product elements – H, O
Step 2: Count the Atoms
Next, count the atoms present in each of the elements. An atom is the smallest particle in an element that contains all its chemical properties. The number of atoms in an element is usually represented by a subscript next to the element’s chemical formula. For example, N2 is a molecule containing two nitrogen atoms. In line with our example, we will get:
- Reactant elements – H (2), O (2)
- Product elements – H (2), O (1)
Step 3: Equalize the Number of Atoms
As you can see, the number of oxygen atoms in the product side is less than the number in the reactant side. This means that the chemical equation is unbalanced and must be balanced per the law of conservation of matter. You can do this by multiplying the number of atoms on each side until they are equal. In our case, we will need to multiply the compound by 2 to form:
H2 + O2 –> 2H2O
This makes the number of oxygen atoms on both sides two but unbalances the hydrogen atoms, which are now two on the reactant side and four in the product. We must now multiply the hydrogen in the reactant side by two to make the atoms four.
Note: The coefficient used to multiply the atoms during the balancing is usually placed before the atom or compound, not as a subscript.
Step 4: Supply the Coefficients
Now, supply the coefficients (the numbers with which you multiplied the atoms in step 3) into the equation. Note that the number is placed in front of a compound even if only one element in that compound was multiplied. You should end up with:
2H2O + O2 –> 2H20
Step 5: Count the Molecules
Lastly, count the atoms on both sides for each element to see if they balance. We now have:
- Reactant elements – H (4), O (2)
- Product element – H (4), O (2)
As you can see, the atoms are equal on both sides. The equation is now balanced. If the number of atoms in your equation is not equal, you should redo your multiplication.
Methods for Balancing Chemical Equations
Generally, there are two ways you can balance a chemical equation. These are:
Combustion Reaction Method
The combustion reaction method is used to balance equations with oxygen on both the reactant and product sides. It allows you to use ½ fractions to balance the oxygen atoms then double them, in the end, to come up with whole-number coefficients.
Proportion Method
The proportion method is used to balance complex chemical equations that are difficult to understand at a glance. Such equations usually contain many subscripts, so you should be careful when supplying coefficients.
Why Is It Important to Balance the Chemical Equations?
The law of conservation of mass was established in 1789 by Antoine Laurent and implies that the quantity of matter should be equal before and after a chemical reaction. This law is the main reason chemical equations should be balanced; else, they do not represent accurate reactions. Besides this, balancing equations is a crucial step in determining the number of reactants that should be used to prepare a given product. The product will not form if the mole ratios are off.
Types of Chemical Equations
There are five types of chemical reactions and equations that represent them. They are:
Displacement Reaction
A displacement reaction can be single or double. A single displacement reaction involves a product where one chemical compound from the reactant side exchanges to the product. In a double displacement reaction, two sets of exchanges happened. Here are some examples:
1. Zn + H2SO4 –> ZnSO4 + H2
2. 2NaCl + CaC03 –> Na2CO3 + CaCl2
In the first reaction, zinc displaces the hydrogen in sulfuric acid to form a compound, zinc sulfate. Since only one cation is being exchanged, this is a sing displacement reaction. The second reaction is double displacement because both reactants exchange anions in the product.
Combination or Synthesis Chemical Reaction
Combination chemical reactions are the most common chemical reactions. They happen when two or three reactants combine to form a new product (e.g., 2H2 + O2 – 2H20).
Decomposition Chemical Reaction
A decomposition chemical reaction happens when one compound decomposes into two or more products, e.g., Ca(NO3)2 – > CaO + NO2 + 02. This reaction involves the application of heat to calcium nitrate to decompose it into calcium oxide, nitrogen (i) oxide, and oxygen gas.
Combustion Reaction
A combustion reaction happens when a compound of carbon and a compound of oxygen combine to form water and carbon (iv) oxide and a third product.
Acid-Base Reaction
Also called a neutralization reaction, this is the reaction between an acid and a base to form salt and water (e.g., MgO + H2SO4 –> MgSO4 + H2O)
Tips for Balancing the Chemical Equations
Learning to balance chemical equations can seem daunting at the beginning, even with all this information. Here are some additional tips to help you get better at this skill:
If a compound contains multiple ions, you should balance it as a unit. For example, CO3 (carbonate) should be balanced as a whole, not as carbon and oxygen.
Never change the value of the subscript in a compound or element. You can only change the coefficient in front of the chemical formula.
Always start balancing the product or reactant with the highest number of atoms that are not oxygen or hydrogen.
Always ensure that the coefficients used to balance your equation are in the lowest term possible (and not fractions).
Frequently Asked Questions
What are the four rules for balancing equations?
When balancing equations:
- Only change the coefficients; not the subscripts
- Never leave an equation with fractional coefficients
- Only use fractional coefficients when it makes sense at the atom level
- Use the lowest term of a coefficient
Can you use halves when balancing equations?
Yes. You can use fraction coefficients to balance a chemical equation as long as it makes sense at the atom level. If a fractional coefficient gives you a fraction of an atom, it is incorrect.
Can a balanced equation have fractions?
No, a balanced equation should never have fractions. If you use fractional coefficients to balance an equation, you should multiply the equation with the denominator of the fraction at the end to turn them into whole numbers.
Key Points
A chemical equation represents a reaction between given elements or compounds to form a chemical product. Per the law of conservation of mass, the reactants and products in a reaction should be of the same mass, which means chemical equations should always be balanced. An equation is balanced when the number of elements or molecules on the reactant side is equal to that of the product. You can practice balancing equations through Balancing Chemical Equations Worksheets.
