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Analytical Chemistry: Volumetric Analysis Lecture 2
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Analytical Chemistry: Volumetric Analysis Lecture 2

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Questions and Answers

A weak acid has a strong conjugate base.

True

The equilibrium of a strong acid lies far to the left.

False

Phosphoric acid (H3PO4) is a strong acid.

False

The pH of a 0.10M solution of HCl is 2.

<p>False</p> Signup and view all the answers

The pH of a strong acid solution can be calculated using the formula pH = -log [H+].

<p>True</p> Signup and view all the answers

Weak acids dissociate completely in water.

<p>False</p> Signup and view all the answers

The concentration of OH- (aq) is directly proportional to the concentration of H+ (aq).

<p>False</p> Signup and view all the answers

The pH of a solution can be calculated from the concentration of OH- (aq).

<p>True</p> Signup and view all the answers

H2SO4 is a weak acid.

<p>False</p> Signup and view all the answers

The pH of an aqueous solution with an OH- (aq) concentration of 1.2 x 10-6 M is 9.1.

<p>False</p> Signup and view all the answers

Study Notes

Volumetric Analysis

  • Volumetric analysis involves the calculation of mole fractions of solutes in a solution.
  • A weak acid is a substance that does not completely dissociate in water, such as HF, HClO3, and HF.
  • The mole fraction of a solute can be calculated using the formula: mole fraction = number of moles of solute / total number of moles of solution.

Concentration Units

  • Concentration units include:
    • g/L (grams per liter)
    • ppm (parts per million)
    • ppb (parts per billion)
    • w/w% (weight/weight percentage)
    • w/v% (weight/volume percentage)
  • Conversion between concentration units can be done using the following formulas:
    • ppm = (mass of solute / mass of solution) x 10^6
    • ppb = (mass of solute / mass of solution) x 10^9

Acids and Bases

  • Arrhenius definition:
    • Acids are H+ donors
    • Bases are OH- donors
  • Broadened definition:
    • Acids increase H+ concentration or [H+] increases
    • Bases increase H+ acceptor
  • Arrhenius theory:
    • Acids are substances that increase the concentration of the hydronium ion (H3O+) when dissolved in water
    • Bases are substances that dissociate into hydroxide ions (OH-) and cations in solution
  • Problems with Arrhenius theory:
    • H3O+ is not present in solution, but rather OH(H2O)3-
    • Other substances also have acidic or basic properties

Bronsted-Lowry Theory

  • A Bronsted-Lowry acid is a species that donates a proton (H+)
  • A Bronsted-Lowry base is a substance that can accept a proton (H+)
  • Bronsted-Lowry acid-base theory has several advantages over Arrhenius theory:
    • It can explain the behavior of substances that do not contain OH- or H3O+
    • It can explain the behavior of substances that have multiple acidic or basic properties

Lewis-Lowry Theory

  • A Lewis acid is a chemical compound that has a tendency to accept an electron pair or more from a donor compound
  • A Lewis base is a chemical compound that has a tendency to donate an electron pair to an acceptor compound
  • Examples of Lewis acids and bases include trimethylborane (Me3B) and ammonia (NH3)

The Leveling Effect

  • The level of acidity is governed by acid strength, which is the result of the dissociation of acids in solvents
  • If the acid strength is greater than the solvent strength, the equilibrium will lie towards the right (100% dissociation of the acid)

Acid Strength

  • Acid strength is defined by the equilibrium position of its dissociation reaction
  • A strong acid is one for which the equilibrium lies far to the right (almost all of the original acid is dissociated)
  • A weak acid is one for which the equilibrium lies far to the left (only a small amount of the original acid is dissociated)
  • Examples of strong acids include hydrochloric acid (HCl) and sulfuric acid (H2SO4)
  • Examples of weak acids include phosphoric acid (H3PO4), acetic acid (CH3COOH), and benzoic acid (C6H5COOH)

pH Calculation

  • pH can be calculated using the formula: pH = -log[H3O+] = -log[H+]
  • The pH of a strong acid solution can be calculated using the concentration of the acid
  • The pH of a weak acid solution can be calculated using the equilibrium constant (Ka) and the concentration of the acid

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Description

This quiz is based on the second lecture of Analytical Chemistry, covering topics such as volumetric analysis, weak acids, and mole fraction calculations.

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