Acids, alkalis and salts

• What do acids produce in aqueous solution?

  Hydrogen ions, H+
• What is the pH value of acidic solutions?

  Less than 7
• What do alkalis produce in aqueous solution?

  Hydroxide ions, OH-
• What is the pH value of alkaline solutions?

  Greater than 7
• What is the pH value of a neutral solution?

  7
• What does the pH scale measure?

  The acidity or alkalinity of a solution
• What is an example of an acid-alkali indicator?

  Universal indicator
• What are the colors of red and blue litmus paper in different pH conditions?

  • Red litmus paper:
  • Stays red in acidic
  • Stays red in neutral
  • Turns blue in alkaline
  • Blue litmus paper:
  • Turns red in acidic
  • Stays blue in neutral
  • Stays blue in alkaline
• What is a base?

  A substance that reacts with an acid to form a salt and water
• What are bases that are soluble in water called?

  Alkalis
• What is the general reaction for neutralisation?

  Acid + base → salt + water
• What ions do acids and alkalis provide in a neutralisation reaction?

  Acids provide H+ ions and alkalis provide OH- ions
• What is produced when H+ ions react with OH- ions?

  Water, H2O
• What is produced when acids react with metals?

  A salt and hydrogen gas
• What is the general equation for the reaction of an acid with a metal?

  Acid + metal → salt + hydrogen
• What is the ionic equation for the reaction of magnesium with hydrochloric acid?

  2H+(aq) + Mg(s) → Mg2+(aq) + H2(g)
• What happens to magnesium atoms during the reaction with hydrochloric acid?

  They lose electrons and are oxidised
• What do metal oxides produce when they react with acids?

  A salt and water
• What is the general reaction for acids reacting with carbonates?

  Acid + carbonate → salt + water + carbon dioxide
• What is the first part of a salt's name derived from?

  The base, alkali, or metal carbonate
• What is the second part of a salt's name derived from?

  The acid
• What is the formula for aluminium sulfate?

  Al2(SO4)3
• What are the steps to prepare a soluble salt from an insoluble reactant?

  1. Add powdered insoluble reactant to acid in a beaker, stirring to mix.
  2. Continue adding until in excess.
  3. Filter to remove excess solid.
  4. Heat the solution in an evaporating dish.
  5. Leave to crystallise at room temperature.
  6. Dry the crystals if necessary.
• What is the purpose of using a Bunsen burner in the practical preparation of soluble salts?

  To heat dilute acid
• What is a hazard associated with concentrated hydrochloric acid?

  It is corrosive and can damage skin and clothes
• What is the definition of a concentrated solution?

  A solution containing a relatively large amount of dissolved solute
• What happens to strong acids in solution?

  They completely dissociate into ions
• What is an example of a weak acid?

  Ethanoic acid
• What does the symbol ⇌ indicate in a reaction?

  It shows that the reaction is reversible
• How does the concentration of H+ ions affect the pH of a solution?

  The higher the concentration of H+ ions, the lower the pH
• What happens to the pH if the hydrogen ion concentration increases by a factor of 10?

  The pH decreases by 1 unit
• How does the concentration of OH- ions affect the pH of alkaline solutions?

  The higher the concentration of OH- ions, the higher the pH