Podcast Beta
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.
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The pH of a strong acid solution can be calculated using the formula pH = -log [H+].
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Weak acids dissociate completely in water.
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The concentration of OH- (aq) is directly proportional to the concentration of H+ (aq).
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The pH of a solution can be calculated from the concentration of OH- (aq).
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H2SO4 is a weak acid.
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The pH of an aqueous solution with an OH- (aq) concentration of 1.2 x 10-6 M is 9.1.
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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.