Chemical Reactions and Atomic Theory Fundamentals

1. What is a chemical reaction?

A chemical reaction is a process whereby one or more substances are transformed into different substances.

2. What are the reactants?

Reactants are the original substances present before a chemical reaction occurs.

3. What are the products?

Products are the substances formed as a result of a chemical reaction.

4. Reactants and Products in Carbon Dioxide Formation

In the reaction: Carbon + Oxygen → Carbon Dioxide:

• Reactants: Carbon and Oxygen.
• Product: Carbon Dioxide.

5. Law of Conservation of Mass

1. The mass of a system remains constant, regardless of the transformations that occur within it.
2. In any chemical transformation taking place in a closed system, the total mass of the substances remains unchanged.

6. Mass Calculation Example

If 7 grams of carbon react with 32 grams of oxygen, how many grams of carbon dioxide are produced?

7 g C + 32 g O₂ → 39 g CO₂

7. Percentage Composition of Water

Given 18 grams of water containing 2 grams of hydrogen:

• Hydrogen: (2g / 18g) × 100 ≈ 11.1%
• Oxygen: (16g / 18g) × 100 ≈ 88.9%

8. Dalton's Atomic Theory

1. Matter is composed of indivisible atoms.
2. Atoms remain unchanged during chemical processes.
3. Elements are formed by identical atoms with the same mass and chemical properties.
4. Atoms of different elements possess different masses and chemical properties.
5. Chemical compounds are formed by combining two or more atoms of different elements.
6. Atoms of different elements combine in simple integer ratios to form compounds.
7. In chemical reactions, atoms are neither created nor destroyed; they only change their distribution.

Compound: A substance formed by different atoms combined in fixed proportions.
Chemical reaction: The reorganization of atoms within the substances involved.

9. Avogadro's Law

1. Gas particles are often aggregates of atoms known as molecules.
2. Equal volumes of gases, measured under the same conditions of temperature and pressure, contain an equal number of molecules.

10. What is the mole?

The mole represents a set of 6.022 × 10²³ identical particles. These may be atoms, molecules, ions, electrons, or other specific groupings of matter.