Chemical Reactions And Equations:

Chemical Equations:

Explanation:

Chemical Equations

1. Reactants → Products

• Reactants are the starting substances in a chemical reaction.
• Products are the new substances formed after the reaction.

A chemical equation is written as:$$\textbf{Reactants} \rightarrow \textbf{Products}$$Reactants→Products

The arrow (→) shows the direction of the reaction.

---

2. Important Historical Contributions

• 1774 – Joseph Priestley discovered Oxygen.
• 1789 – Antoine Lavoisier proposed the Law of Conservation of Mass.

These discoveries helped scientists understand how chemical reactions work.

---

3. Balanced Chemical Equation

A balanced equation has:

👉 The same number of atoms of each element on both sides of the equation.

This follows the Law of Conservation of Mass, which states:

Matter is neither created nor destroyed during a chemical reaction.

So,$$\textbf{Mass of Reactants = Mass of Products}$$Mass of Reactants = Mass of Products

---

4. Example

$$O_2 + 2H_2 \rightarrow 2H_2O$$O2​+2H2​→2H2​O

This equation shows:

• Oxygen reacts with Hydrogen
• Water is formed
• The equation is balanced because the number of Hydrogen and Oxygen atoms is equal on both sides.

---

5. Coefficients

• Coefficients are the numbers written in front of chemical formulas.
• They are used to balance equations.
• Example: In 2H₂O, the number 2 is the coefficient.

---

Quick Revision Points

✔ Reactants → Products
✔ Balanced equation = equal atoms on both sides
✔ Law of Conservation of Mass
✔ Coefficients help in balancing