A balanced chemical equation demonstrates the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. In order for a chemical equation to be balanced, the number of atoms of each element must be the same on both the reactant and product sides of the equation.
Here’s how a balanced equation satisfies this law:
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Atoms are Conserved: In a balanced equation, the total number of atoms of each element present in the reactants (the substances that undergo change) is equal to the total number of atoms of those elements in the products (the substances formed as a result of the reaction). This reflects that no atoms are lost or gained during the reaction.
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Mass Corresponds to Atom Count: Since the mass of an object is based on the number and type of atoms it contains, preserving the number of each type of atom means that the total mass of the reactants is equal to the total mass of the products. This further reinforces the concept that the mass is conserved throughout the chemical reaction.
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Example: Consider the combustion of methane represented by the balanced equation: \[ CH_4 + 2 O_2 \rightarrow CO_2 + 2 H_2O \]
- On the left (reactants), there are 1 carbon (C), 4 hydrogen (H), and 4 oxygen (O) atoms.
- On the right (products), there are also 1 carbon (C), 4 hydrogen (H), and 4 oxygen (O) atoms (1 in \(CO_2\) and 2 molecules of \(H_2O\) each contributing 1 oxygen).
- Since the count of each type of atom is the same before and after the reaction, the mass remains constant, illustrating that mass is conserved.
In summary, a balanced chemical equation upholds the law of conservation of mass by ensuring that all atoms in the reactants are accounted for in the products, thereby maintaining the total mass throughout the reaction process.