Analytical Chemistry Lecture 2: Volumetric Analysis

Volumetric Analysis

• Volumetric analysis is a type of analytical chemistry that deals with the measurement of the volume of a solution required to react completely with a known volume of another solution.
• Problems in volumetric analysis include calculating the mole fraction of a substance in a solution, determining the normality of a solution, and expressing the concentration of a solution in different units.

Mole Fraction and Molarity

• The mole fraction of a substance in a solution is the ratio of the number of moles of the substance to the total number of moles of all substances in the solution.
• The molarity of a solution is the number of moles of solute per liter of solution.

Normality and Molarity

• The normality of a solution is the number of equivalents of solute per liter of solution.
• Normality is related to molarity by the formula: Normality = Molarity x Number of equivalents per mole.

Concentration Units

• Concentration units include g/L, ppm, and ppb.
• ppm (parts per million) is a unit of concentration that represents the number of parts of a substance per million parts of a solution.
• ppb (parts per billion) is a unit of concentration that represents the number of parts of a substance per billion parts of a solution.

Acids and Bases

• Acids are substances that donate a proton (H+), while bases are substances that accept a proton.
• The Arrhenius theory of acids and bases defines acids as substances that increase the concentration of H+ in a solution, and bases as substances that increase the concentration of OH- in a solution.

Bronsted-Lowry Theory

• The Bronsted-Lowry theory of acids and bases defines an acid as a substance that donates a proton, and a base as a substance that accepts a proton.
• This theory is an improvement over the Arrhenius theory because it can explain the behavior of acids and bases in non-aqueous solutions.

Lewis Theory

• The Lewis theory of acids and bases defines an acid as a substance that accepts an electron pair, and a base as a substance that donates an electron pair.
• This theory is more general than the Bronsted-Lowry theory because it can explain the behavior of acids and bases in a wide range of solutions.

Leveling Effect

• The leveling effect is the phenomenon where the strength of an acid is determined by the solvent in which it is dissolved.
• In a solvent such as water, the leveling effect causes strong acids to be completely dissociated, while weak acids are only partially dissociated.

Acid Strength

• The strength of an acid is defined by the equilibrium position of its dissociation reaction.
• A strong acid is one that is completely dissociated in a solvent, while a weak acid is one that is only partially dissociated.

pH Calculation

• The pH of a solution is calculated using the formula: pH = -log[H+].
• The pH of a strong acid solution can be calculated using the formula: pH = -log[Concentration of acid].
• The pH of a weak acid solution can be calculated using the formula: pH = -log[Concentration of acid] + pKa.