Page 22 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

Evidence For A Chemical Reaction

1. Evolution of light or heat.

2. Temperature change (increase or decrease) to the surroundings.

3. Formation of a gas (bubbling or an odor) other than boiling.

4. Color change (due to the formation of a new substance).

5. Formation of a precipitate (a new solid forms) from the reaction of two

aqueous solutions.

Chemical Equations

• Chemical equations are used to represent or describe chemical reactions.

• For example: when hydrogen (H 2) burns, it reacts with oxygen (O 2) in the air
to form water.

• We write the chemical equation for this reaction as follows:

2H2 + O2 → 2H2O

An equation shows…

• Formulas of reactants

• Formulas of products

• Molar ratios of all compounds in the reaction.

• To add more information to the equation, you can indicate the physical

states of substances by putting a symbol after each formula.

• Use (s) for a solid, (l) for a liquid, (g) for a gas, and (aq) for a substance in

an aqueous solution (a substance dissolved in water).

Fe(s) + O2(g) → Fe2O3(s)

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