What is a chemical equation in which mass is conserved and each side of the equation has the same number of atoms?
A chemical equation in which mass is conserved and each side of the equation has the same number of atoms is known as a balanced chemical equation.
Understanding Balanced Chemical Equations
A balanced chemical equation is a fundamental concept in chemistry that adheres to the Law of Conservation of Mass. This law states that mass is neither created nor destroyed in a chemical reaction. Therefore, the total mass of the reactants must equal the total mass of the products. For this to occur, the number of atoms of each element must be identical on both sides of the equation.
Key Characteristics
A balanced chemical equation possesses several defining features:
- Mass Conservation: The total mass of all reactants equals the total mass of all products.
- Atom Conservation: There are an equal number of atoms of each specific element on the reactant side (left) and the product side (right) of the equation.
- Use of Coefficients: To balance an equation, a coefficient – a small whole number – is placed in front of a chemical formula. These coefficients adjust the number of molecules or formula units involved in the reaction without changing the chemical identity of the substances.
How to Balance a Chemical Equation
Balancing a chemical equation involves adjusting coefficients to satisfy the Law of Conservation of Mass. Here are the general steps:
- Write the Unbalanced Equation: Begin by writing the chemical formulas for all reactants and products.
- Count Atoms: Count the number of atoms for each element on both the reactant and product sides.
- Add Coefficients: Place coefficients in front of the chemical formulas to balance the number of atoms for each element. It's often helpful to balance elements that appear in only one reactant and one product first. Polyatomic ions can sometimes be balanced as a unit.
- Verify: Re-count the atoms of each element on both sides to ensure they are equal.
For a detailed guide on balancing chemical equations, you can explore resources like Khan Academy's tutorial on balancing chemical equations.
Example of a Balanced Chemical Equation
Let's consider the reaction of hydrogen gas ($\text{H}_2$) with oxygen gas ($\text{O}_2$) to form water ($\text{H}_2\text{O}$).
1. Unbalanced Equation:
$\text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O}$
2. Atom Count (Unbalanced):
| Element | Reactants | Products |
|---|---|---|
| Hydrogen | 2 | 2 |
| Oxygen | 2 | 1 |
As you can see, the oxygen atoms are not balanced.
3. Balanced Equation:
To balance the oxygen atoms, we place a coefficient of 2 in front of $\text{H}_2\text{O}$ on the product side:
$\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$
Now, let's re-count:
| Element | Reactants | Products |
|---|---|---|
| Hydrogen | 2 | 4 (2 molecules of $\text{H}_2\text{O}$ means 2x2=4 H atoms) |
| Oxygen | 2 | 2 (2 molecules of $\text{H}_2\text{O}$ means 2x1=2 O atoms) |
The hydrogen atoms are now unbalanced. To balance the hydrogen, we place a coefficient of 2 in front of $\text{H}_2$ on the reactant side:
$2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$
4. Final Atom Count (Balanced):
| Element | Reactants | Products |
|---|---|---|
| Hydrogen | 4 (2 molecules of $\text{H}_2$ means 2x2=4 H atoms) | 4 (2 molecules of $\text{H}_2\text{O}$ means 2x2=4 H atoms) |
| Oxygen | 2 | 2 (2 molecules of $\text{H}_2\text{O}$ means 2x1=2 O atoms) |
This final equation is a balanced chemical equation because both mass and the number of atoms for each element are conserved on both sides.
