Stoichiometry - Pronunciation "stoy·kee·o·muh·tree"
There are two fundamental, linked principles in chemistry:
Law of Conservation of Mass : This law states that in any closed system, the total mass of the reactants before a chemical reaction must equal the total mass of the products after the reaction. Atoms are neither created nor destroyed, but simply rearranged into different compounds
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"Adding up" in Balanced Equations : Chemical equations are "balanced" precisely to reflect this law. The stoichiometric coefficients (the numbers in front of the chemical formulas) are adjusted so that the number of atoms of each element is identical on both the reactant and product sides of the equation. For example:
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Unbalanced : H2 + O2 → H2O
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Balanced : 2H2 + O2 → 2H2O
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In the balanced equation, there are 4 hydrogen atoms and 2 oxygen atoms on both sides. This ensures that the mass "adds up" perfectly
Law of Definite Proportions : This law (also known as the Law of Constant Composition) states that a given chemical compound always contains its constituent elements in a fixed, constant ratio by mass, regardless of the source or method of preparation.
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"Adding up" within a Formula : A chemical formula, such as H2O, indicates a fixed ratio of atoms (two hydrogen atoms for every one oxygen atom) and thus a fixed mass ratio (approximately 1:8 by mass). This fixed composition is what makes a compound a distinct substance; mixing elements in different ratios results in a different substance or a mixture with leftover reactants.
Summary : The "perfect accuracy" in chemical formulas and equations stems from the fact that matter is composed of discrete, unchangeable atoms that combine in consistent, simple whole-number ratios. These fundamental laws allow for precise quantitative predictions in chemical reactions, a field known as stoichiometry in GCSE Chemistry. The real father of chemistry Antoine Lavoisier, whose experiments supported the law of conservation of mass. Antoine Lavoisier created the first list of fundamental elements that “are the substances we have not discovered means for separating”.
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