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 happens to the pH as it decreases?

  The solution becomes more acidic
• How does the strength of an acid relate to its pH?

  Lower pH means stronger acid
• What is an alkali?

  A base that dissolves in water
• What is the relationship between pH and H⁺ concentration?

  Decreasing pH increases concentration
• What do acidic solutions release in water?

  Hydrogen ions, H
• What distinguishes a strong acid from a weak acid?

  Strong acids completely dissociate in solution
• Name a strong acid.

  Hydrochloric acid
• What do alkali solutions contain?

  Hydroxide ions, OH
• How do strong bases behave in solution?

  They fully dissociate to release OH^- ions
• What is the difference between dilute and concentrated solutions?

  Dilute refers to amount of substance present
• What does weak/strong refer to in acids and bases?

  Degree of ionisation of the acid or base
• What is the general reaction of an acid with a metal?

  Acid + metal → salt + hydrogen
• What determines the reaction of an acid with a metal?

  The reactivity of the metal
• What is produced in a neutralisation reaction?

  Salt and water
• What is the general equation for neutralisation?

  Acid + alkali → salt + water
• What does sulfuric acid produce when reacted?

  Sulfates
• How do you 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. Evaporate water from salt solution
  6. Leave to evaporate slowly for crystals
• What is a precipitation reaction used for?

  To make insoluble salts
• What is the first step in a precipitation reaction?

  React two solutions containing desired ions
• What are the steps to prepare insoluble salts?

  1. React two solutions with desired ions
  2. A solid precipitate forms
  3. Filter the salt out
  4. Wash with distilled water
  5. Leave to dry on filter paper
• What is the purpose of titration?

  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
  3. Add indicator and place flask on white tile
  4. Slowly add acid until neutralisation point
  5. Calculate the volume of acid (titre)
  6. Repeat for concordant titres
• What does phenolphthalein indicate in a titration?

  It changes from pink to colourless
• What is the definition of concordant titres?

  Titres within 0.1 cm of each other
• How do you calculate the mean titre?

  Use all concordant results to calculate
• How do you calculate the concentration of alkali from acid concentration?

  Use moles and mole ratio from reaction
• What is the unit of concentration when calculated in titration?

  mol dm
• 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 reacted 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
• What does the pH scale measure?

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

  pH 7

  
• What happens to pH as acidity increases?

  pH decreases
• How does the pH scale relate to acid strength?

  The lower the pH, the stronger the acid
• What is an alkali?

  A base that dissolves in water