CLASS 8 · LEARNING KNOWLEDGE
Balancing reaction equations – basic principles
How it works
When balancing reaction equations, it is ensured that the same number of atoms of each type are present on both sides of the equation. The law of conservation of mass states that atoms are neither created nor destroyed. Therefore, reactants and products must contain the same number of atoms. This is done by adjusting the so-called stoichiometric coefficients in front of the chemical formulas, not by changing the formulas themselves.
Note
When balancing chemical reaction equations, the coefficients are chosen so that the number of each element is the same on both sides of the equation.
When balancing chemical reaction equations, the coefficients are chosen so that the number of each element is the same on both sides of the equation.
An example
What number must be placed in front of the molecule O2 so that the equation H2 + O2 → H2O is balanced?
On the left there are 2 hydrogen atoms and 2 oxygen atoms, on the right 2 hydrogen atom and 1 oxygen atom. So oxygen atoms are missing on the right. If a 2 is placed in front of H2O and a 2 in front of H2 as well, the result is: 2 H2 + O2 → 2 H2O. So no number has to be placed in front of O2 (implicitly 1).
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50 Exercises
To the learning unit →Own explanation and own practice exercises by AmyMath. Subject reference framework: Chemistry. The topic assignment may vary by federal state.