General Chemistry PHARM-101 Quiz

General Chemistry for Pharmaceutical Sciences (PHARM-101)

• Course presented by Dr. Azza H. Rageh, Associate Professor of Pharmaceutical Analytical Chemistry at Taibah University.

Stoichiometry, Solution Concentration and Chemical Reactions

• Stoichiometry is the calculation of reactant and product quantities in a chemical reaction.
• Stoichiometry can predict the products' quantities based on reactants' amounts.
• Stoichiometry can determine the necessary reactants to produce a desired product amount.
• Coefficients in a balanced chemical equation define relative amounts (in moles) of substances involved.

Reaction Stoichiometry

• Example: 2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O
• 2 molecules of C₈H₁₈ react with 25 molecules of O₂ to form 16 molecules of CO₂ and 18 molecules of H₂O.
• Alternatively, 2 moles of C₈H₁₈ react with 25 moles of O₂ to form 16 moles of CO₂ and 18 moles of H₂O.
• Stoichiometric Ratio: The ratio of moles between components in a balanced equation (e.g., 2 mol C₈H₁₈ : 16 mol CO₂).

Concentration of Solutions

• Concentration: the amount of solute present in a solution.
• Units: percent weight (% w/w), percent volume (% v/v), percent weight per volume (% w/v), parts per million (ppm), parts per billion (ppb), molarity (M), formality (F), normality (N), and molality (m).
• Definitions:
  • Solvent: the component present in the largest amount.
  • Solute: the other components.
  • Solution: a homogeneous mixture.

Molarity

• Molarity (M): moles of solute per liter of solution.
• Formula: M = moles of solute / Liters of solution
• Unit: mol/L or mol⋅L⁻¹ or molar

Types of Aqueous Solutions and Solubility

• Salt water: homogeneous mixture of NaCl and H₂O.
• Sugar water: homogeneous mixture of C₁₂H₂₂O₁₁ and H₂O.
• Solids dissolve in water due to attractive forces between solute and solvent particles.

What Happens When a Solute Dissolves?

• Solute particles attract each other. Solvent molecules attract each other.
• When mixing solute and solvent, attractive forces occur between solute and solvent particles.
• Strong attractions lead to successful dissolution.

Dissolution of Sodium Chloride in Water

• Ionic compounds (like salt) in water dissociate into ions.
• Water molecules pull the ions off the crystal.

Dissolving of Sugar in Water

• Sugar molecules mix homogeneously with water molecules.
• Sugar doesn't dissociate into ions in water.
• Solutions of sugar do not conduct electricity.

Electrolytes and Nonelectrolytes

• Electrolytes: substances that dissolve in water to create solutions conducting electricity.
• Strong electrolytes completely ionize in water, conduct electricity strongly (e.g., soluble ionic salts, strong acids, strong bases).
• Weak electrolytes partially ionize in water, conduct electricity weakly (e.g., weak acids, weak bases).
• Nonelectrolytes don't ionize in water, don't conduct electricity (e.g., molecular substances, like sugar and alcohol).

Basic Types of Chemical Reactions

• Synthesis reaction: two or more reactants combine to form one product (A + B → AB).
• Decomposition reaction: a more complex substance breaks down into simpler parts (AB → A + B).
• Replacement reaction:
  • Single replacement: one element replaces another in a compound (A + BC → AC + B).
  • Double replacement: anions and cations of two compounds switch places (AB + CD → AD + CB).

Chemical Reactions between Ions

• Ions form water, weak electrolytes, precipitates, gases, or complex ions.

Formation of Water

• Reaction between metallic hydroxide (including ammonium hydroxide) and an acid; produces water.

Formation of Weak Electrolyte

• Reaction between strong acid and salt containing weak acid anion; yields weak acid.
• Reaction between strong base and ammonium salt; produces weak base (ammonia hydroxide).

Formation of a Precipitate

• Precipitation: formation of a solid in a solution during a chemical reaction.
• Occurs when dissolved ions exceed solubility limit, forming insoluble salt.
• Can be accelerated by adding a precipitating agent or removing solvent.

Formation of a Gas

• Ions may produce gas evolution when the product is gaseous or product is unstable and decomposes to form a gas.

Formation of Complex Ions

• Complexation reaction: a reaction between a Lewis acid (electron acceptor) and a Lewis base (electron donor).
• Ligands bond with a metal atom to form a complex.

Reactions Involving Oxidation-Reduction (Redox)

• Redox reactions involve electron transfer.
• Oxidation: loss of electrons.
• Reduction: gain of electrons.
• Other common redox reactions include rusting of iron, combustion of octane, and combustion of hydrogen.

Oxidizing and Reducing Agents

• Oxidizing agent (oxidant): substance causing oxidation of another; itself is reduced.
• Reducing agent (reductant): substance causing reduction of another; itself is oxidized.