Acids and bases

• What do acid-base equilibria involve?

  Transfer of protons between substances
• How are substances classified as acids or bases?

  Based on their interaction with protons
• What is a Brønsted-Lowry acid?

  A proton donor
• What is a Brønsted-Lowry base?

  A proton acceptor
• What does acid strength refer to?

  It does not refer to concentration
• How is a strong acid defined?

  Completely dissociates to ions in solution

  
• What is the pH range of a strong acid?

  pH 0-1
• How is a weak acid defined?

  Only slightly dissociates in solution

  
• What is the pH range of a weak acid?

  pH 3-5
• What is the pH range of strong bases?

  pH 12-14
• What is the pH range of weak bases?

  pH 9-11
• What does pH measure?

  Acidity and alkalinity
• What type of scale is pH?

  A logarithmic scale from 0 to 14

  
• What does a pH of 0 indicate?

  An acidic solution with high H$^+$ concentration
• What does a pH of 14 indicate?

  A basic solution with low H$^+$ concentration
• How can the concentration of H$^+$ ions be determined?


  Using the pH value
• What is the ionic product of water?

  Water slightly dissociates to ions
• What is the value of Kw at 25°C?

  1 x 10$^{-14}$
• How does temperature affect Kw?

  Kw changes as temperature changes
• What type of reaction is the forward reaction in water's equilibrium?

  Endothermic reaction
• What happens to H$^+$ ions as temperature increases?


  More H$^+$ ions are produced
• What is the equilibrium dissociation constant for weak acids and bases?

  Ka

  
• How can pKa be used?

  To find the concentration of weak acids
• What is the relationship between Ka, pKa, and [H$^+$]?


  They can be used to find pH
• What method is used when HA is in excess?

  Use [HA] and [A$^-$] with Ka
• What method is used when A$^-$ is in excess?


  Use Kw to find [H$^+$]
• What happens when HA = A$^-$?


  pKa is equal to pH

  
• What does a pH titration curve show?

  How pH changes during an acid-base reaction

  
• What is the neutralisation point in a titration curve?

  A large vertical section through the equivalence point
• How is a titration curve investigated?

  By slowly adding alkali to an acid

  
• What is the effect of smaller added volumes in titration?

  More accurate curve produced
• What is the neutralisation point for a strong acid-strong base reaction?

  Occurs around pH 7
• What is the neutralisation point for a strong acid-weak base reaction?

  Less than pH 7 (more acidic)
• What is the neutralisation point for a weak acid-strong base reaction?

  Greater than pH 7 (more basic)
• What is the neutralisation point for a weak acid-weak base reaction?

  Normally pH 7 but hard to determine
• Why are specific indicators used in titrations?

  They indicate pH change within a certain range

  
• What are the two common indicators used at A-Level?

  Methyl orange and phenolphthalein
• What is the color change of methyl orange in acids?

  Orange in acids, yellow at neutralisation
• What is the color change of phenolphthalein in alkalis?

  Pink in alkalis, colorless at neutralisation
• What is a buffer solution?

  A solution that resists pH changes