Acids, Bases + Buffers

• What is a Bronsted-Lowry acid?

  Proton donor
• What is a Bronsted-Lowry base?

  Proton acceptor
• What is a Lewis acid?

  Electron pair acceptor
• What is a Lewis base?

  Electron pair donor
• What ion causes a solution to become acidic?

  H+ (hydrogen ion)

  
• What is the formula for the oxonium ion?

  H3O+
• What ion causes a solution to become alkaline?

  OH- (hydroxide ion)
• Write an equation for the ionisation of water.

  2H2O (l) ⇌ H3O+ (aq) + OH- (aq)
• Give an example of a monobasic acid.

  HCl
• Give an example of a dibasic acid.

  H2SO4
• Give an example of a tribasic acid.

  H3PO4
• Identify the acid-base pairs in the reaction: CH3COOH + H2O ⇌ CH3COO- + H3O+.

  Acid 1: CH3COOH, Base 1: H2O, Base 2: CH3COO-, Acid 2: H3O+
• What defines a strong acid?

  Acids dissociate completely
• Give examples of strong acids.

  Hydrochloric acid, Sulfuric acid, Nitric acid
• What is the difference between concentrated and strong acids?

  Concentrated means many mol per dm3
• Define weak acids.

  Acids that only partially dissociate
• Give examples of weak acids.

  Methanoic acid, any organic acid
• What is the constant used to measure the extent of acid dissociation called?

  Acid dissociation constant
• What is the symbol of the acid dissociation constant?

  Ka

  
• Write the acid dissociation constant expression.

  Ka = [H+][A-]/[HA]

  
• What does a larger Ka value mean?

  Larger the Ka - greater the extent of dissociation
• Write the equation used to convert Ka into pKa.

  pKa = -log10Ka

  
• Write the equation used to convert pKa into Ka.

  Ka = 10^-pKa
• What is the relationship between pKa and strength of the acid?

  Smaller the pKa stronger the acid
• Write the equation used to convert concentration of H+ into pH.

  pH = -log[H+]

  
• Write the equation used to convert pH into concentration of H+.

  [H+] = 10^-pH
• Why is a pH scale useful compared to concentration of H+?

  pH scale expresses a wide range simply

  
• What is the relationship between pH and [H+]?

  High pH value means a small [H+]
• If two solutions have a pH difference of 1, what is the difference in [H+]?

  A factor of 10
• What is [H+] of a strong acid equal to?

  [H+] = [HA]
• Write the equation used to calculate [H+] of weak acids.

  Use Ka expression

  
• What is the assumption made when calculating pH of weak acids?

  Concentration of acid at equilibrium equals initial concentration

  
• Write the expression for the ionic product of water, Kw.

  Kw = [H+][OH-]
• What are the units for Kw?

  mol²dm^-6
• What is the value of Kw at 298 K?

  1. 0 x 10^-14
• What physical factors affect the value of Kw?

  Temperature affects Kw value
• How does temperature affect Kw?

  If temperature increases, Kw increases
• Indices of [H+] and [OH-] always add up to what value?

  • 14
• Define the term strong base.

  Base that dissociates 100% in water
• Give examples of some strong bases.

  NaOH, KOH, Ca(OH)2