Balancing Chemical Equations (Simplified): Videos & Practice Problems

Balancing chemical equations is essential to ensure that the law of conservation of mass is upheld, meaning the type and number of atoms must be equal on both sides of the reaction arrow. In a balanced equation, the numbers preceding the chemical formulas, known as coefficients, indicate how many molecules of each substance are involved in the reaction. For example, in a balanced equation, coefficients such as 2, 1, and 2 can be used to represent the quantities of reactants and products.

When balancing, it is crucial to distribute these coefficients correctly to account for the total number of atoms. For instance, if a coefficient of 2 is applied to a molecule containing hydrogen, it means that the total number of hydrogen atoms is doubled. If there are already 2 hydrogen atoms in the molecule, the calculation would be 2 (coefficient) times 2 (existing atoms), resulting in 4 hydrogen atoms. Similarly, if the coefficient for oxygen is 1, it remains unchanged, yielding 2 oxygen atoms when multiplied by the coefficient of 2.

On the product side, the same distribution applies. If there are 2 hydrogen molecules, the total becomes 4 hydrogen atoms, and if there is 1 oxygen molecule, it contributes 2 oxygen atoms when multiplied by the coefficient. Thus, the balanced equation confirms that the types of atoms (hydrogen and oxygen) and their respective quantities (4 hydrogens and 2 oxygens) are equal on both sides of the equation.

In summary, balancing chemical equations involves ensuring that the coefficients accurately reflect the number of each type of atom present in the reactants and products, thereby maintaining the integrity of the chemical reaction.

To balance the chemical equation for the combustion of butane (C₄H₁₀), we start by identifying the reactants and products involved. The reactants are butane and oxygen (O₂), while the products are water (H₂O) and carbon dioxide (CO₂).

Initially, we list the number of each type of atom present in the reactants and products. In butane, there are 4 carbon atoms, 10 hydrogen atoms, and 2 oxygen atoms. In the products, we have 1 carbon atom, 2 hydrogen atoms, and a total of 3 oxygen atoms (1 from water and 2 from carbon dioxide). This shows that the equation is unbalanced.

To balance the equation, we proceed by adjusting the coefficients. Starting with carbon, we place a coefficient of 4 in front of CO₂ to balance the carbon atoms, resulting in 4 carbon atoms on both sides. This adjustment also changes the total number of oxygen atoms on the product side to 9 (4 from CO₂ and 1 from H₂O).

Next, we address the hydrogen atoms. Since there are 10 hydrogen atoms in butane, we place a coefficient of 5 in front of H₂O, which gives us 10 hydrogen atoms on the product side as well. This adjustment adds 5 more oxygen atoms, bringing the total to 14 oxygen atoms on the product side.

Now, we need to balance the oxygen atoms. The reactants currently have 2 oxygen atoms from O₂. To achieve a total of 14 oxygen atoms on the reactant side, we need to find a suitable coefficient for O₂. Testing values, we find that a coefficient of 6.5 gives us the required 13 oxygen atoms (6.5 × 2 = 13). However, since we cannot have fractions in our coefficients, we multiply the entire equation by 2 to eliminate the decimal.

After multiplying, the balanced equation becomes:

2 C₄H₁₀ + 13 O₂ → 10 H₂O + 8 CO₂

Thus, the final coefficients for the balanced equation are 2 for butane, 13 for oxygen, 10 for water, and 8 for carbon dioxide. This ensures that the number of each type of atom is equal on both sides of the equation, confirming that the reaction is balanced.