Balancing Chemical Equations Worksheet with Answers

Balancing Chemical Equations Worksheet with Answers

Here you will find Balancing Chemical Equations Worksheet with Answers.

How to Balance Chemical Reactions

Let us begin by defining terms that are relevant to chemical reactions.

A chemical change occurs when a new substance is formed with a different composition.
An example of a chemical change is when carbon (C) and diatomic oxygen gas (O2) get together to form a new gas called carbon dioxide (CO2). At the molecular level, two oxygen atoms are bound to each carbon atom in carbon dioxide. The composition of carbon dioxide is thus different from that of separate carbon and oxygen atoms.

A chemical reaction occurs when two or more substances undergo mutual chemical changes.
An example of a chemical reaction is the synthesis of sodium chloride (NaCl) from sodium (Na) and diatomic chlorine gas (Cl2). In this case, sodium, chlorine, and sodium chloride undergo mutual chemical changes. The separate Na atoms and Cl2 molecules change chemical composition in forming NaCl molecules.

The reactants of a chemical reaction are the initial substances. They react together to produce new substances with different compositions.

The products of a chemical reaction are the final substances. They are the new substances that are produced by the reaction.

For example, in photosynthesis, plants combine water (H2O) and carbon dioxide (CO2) to form carbohydrates, such as glucose (C6H12O6), and diatomic oxygen gas (O2). Water and carbon dioxide are the reactants (these substances react together), while glucose and diatomic oxygen gas are the products (these substances are formed by the reaction).

A chemical equation represents a chemical reaction in symbolic form, with the reactants added together on the left-hand side, the products added together on the right-hand side, and a yield symbol (–>) in between.

An example of a chemical equation is:

NaOH + HCl → NaCl + H2O

The above chemical equation represents the following chemical reaction: Sodium hydroxide (NaOH) reacts together with hydrochloric acid (HCl) to yield sodium chloride (NaCl) and water (H2O).

The reactants are NaOH and HCl, while the products are NaCl and H2O.

The terms of a chemical reaction are separated by plus (+) and yield (-) signs.

For example, consider the following chemical reaction:

FeS + 2 HCl → FeCl2 + H2S

The above chemical equation consists of 4 terms: FeS, 2 HCl, FeCl2, and H2S

A coefficient is a number indicating how much of a substance there is. The coefficient multiplies the number of atoms in a molecule. The coefficient appears to the left of the molecule.

For example, in 7 Al2(SO4)3, the number 7 is a coefficient. It indicates that there are 7 aluminum sulfate molecules. The 7 multiplies each atom in the term.

A chemical reaction is said to be balanced when there are the same number of each type of atom on both sides of the chemical equation.

For example, the following chemical equation is balanced:

2 Cu2S + 3 O2 → 2 Cu2O + 2 SO2

According to the law of conservation of mass, atoms are neither created nor destroyed during a chemical reaction. This is why chemical reactions need to be balanced: to ensure that the reaction has the same number of each type of atom on both sides of the chemical equation. The law of conservation of mass applies to ordinary chemical reactions.

The Significance of Balancing Reactions

The significance of a balanced chemical equation is that the relative amounts of the reactants and products come in the same proportion as the coefficients in the chemical equation. This way, chemists can prepare the right amount of reactants in the laboratory in order to form the desired amount of products.
For example, consider the following chemical reaction:

2 Na + F2 → 2 NaF

According to the above chemical equation, 2 sodium (Na) atoms react with one diatomic fluorine molecule (F2) to yield 2 sodium fluoride (NaF) molecules. Because the proportions are the same at any scale, the same chemical equation tells us that 2 moles of sodium react with one mole of diatomic fluorine gas to yield 2 moles of sodium fluoride, for example.

Balancing Strategy (in Words)

Goal: Add coefficients to each term, as needed, such that the total number of each atom on both sides of the chemical equation matches up exactly.

Steps: Follow these guidelines to balance a chemical reaction:

• Begin by counting the number of each type of atom on each side of the chemical equation.
• Insert one coefficient at a time, attempting to balance one element at a time.
• Work with elements that appear in compounds like NaCl or H2O before working with elements that appear isolated like N2 or Al
• Work with elements that appear only once on each side of the equation before dealing with elements that appear two or more times on the same side.
• It’s generally better to save H and O for last.
• Realize that you may need to change inserted coefficients over the course of balancing a chemical reaction.
• Use trial and error. It’s okay to make a mistake. If something doesn’t work out, you can always go back and change it, and try something else instead.
• If you find yourself needing to insert a fractional coefficient at the end, multiply every coefficient by the denominator of that fraction.

Check: When you finish balancing a chemical equation, add up the total number of each atom on each side to make sure they are the same on both sides.