Acids, Bases and Salts

• What does the pH scale measure?

  Acidity or alkalinity of a solution
• What is the pH value of a neutral solution?


  7

  
• What does a pH less than 7 indicate?


  The solution is acidic
• How does pH relate to acid strength?

  The lower the pH, the stronger the acid
• What does a pH greater than 7 indicate?


  The solution is alkaline or basic
• How does pH relate to alkali strength?

  The higher the pH, the stronger the alkali
• What happens to H⁺ concentration as pH decreases?

  It increases by a factor of 10
• What is an alkali?

  A base that dissolves in water
• What do acidic solutions release in solution?

  Hydrogen ions, H⁺
• What characterizes a strong acid?


  It completely dissociates to release H+ ions
• What characterizes a weak acid?

  It partially dissociates to release H+ ions
• What do alkali solutions contain?

  Hydroxide ions, OH-
• What characterizes a strong base?

  It fully dissociates to release OH- ions
• What characterizes a weak base?


  It partially dissociates to release OH- ions
• How do we describe acids and bases?

  • Strong/weak: degree of ionization
  • Dilute/concentrated: amount of substance present
• What is the general reaction of dilute acid with metals?

  Acid + metal → salt + hydrogen
• What do neutralization reactions produce?

  Salt and water
• What is the reaction of acid with metal carbonate?

  Acid + metal carbonate → salt + water + carbon dioxide
• What determines the salt produced in a reaction?

  The acid used and positive ions in the base
• What is the neutralization reaction of hydrogen ions and hydroxide ions?

  H⁺ (aq) + OH^- (aq) → H₂O (l)
• What does hydrochloric acid produce?

  Chlorides
• What does nitric acid produce?

  Nitrates
• What does sulfuric acid produce?

  Sulfates
• What is the first part of the salt name derived from?

  The positive ions in the base or alkali
• What is the process to prepare soluble salts?

  React acids with solid insoluble substances
• What are the steps to prepare soluble salts?

  1. Measure a set volume of acid
  2. Heat the acid gently
  3. Add chosen base in excess
  4. Filter excess base
  5. Heat salt solution to evaporate water
  6. Leave to evaporate slowly for crystals
• What is a precipitation reaction used for?

  To make insoluble salts
• What are the steps to prepare insoluble salts?

  1. React 2 solutions containing desired ions
  2. A solid precipitate is produced
  3. Filter the salt out
  4. Wash with distilled water and dry
• What is titration used for?

  To measure volumes of acid and alkali
• What are the steps to carry out a titration?

  1. Add acid to burette and record start volume
  2. Add known volume of alkali to conical flask with indicator
  3. Place flask on white tile for visibility
  4. Slowly add acid until neutralisation point
  5. Calculate the volume of acid (titre)
  6. Repeat for concordant titres
• What is the purpose of using an indicator in titration?


  To show the neutralisation point
• What color change indicates neutralisation with phenolphthalein?


  Pink to colourless
• What is the mean titre in titration?

  The average of concordant results
• How do you calculate the concentration of alkali from acid concentration?

  Use mole ratio and balanced equation
• What is the unit of concentration when calculated in titration?

  mol dm-3
• How can you test for carbon dioxide gas?


  Bubble through limewater
• What happens to limewater when carbon dioxide is present?


  It turns milky or cloudy
• What do carbonates produce when reacting with dilute acids?

  Carbon dioxide gas
• What is the test for sulfate ions?

  Add dilute hydrochloric acid and barium chloride
• What indicates the presence of sulfate ions in a solution?


  A white precipitate forms