Acids and Bases

• Acidic solutions have more H+ than OH-, resulting in a lower pH value.
• Acids release H+
• Neutral substances are neither acidic nor basic, with equal amounts of H+ and OH-. They have a neutral pH (7).
• Alkalis release OH- ions when dissolved in water.
• Bronstead Lowry - an acid is a proton donor.
• Bronstead Lowry - a base is a proton acceptor.
• Metal oxides, metal hydroxides, metal carbonates, and ammonia are classified as bases.
• Bases neutralise acids to form water and a salt.
• Acid + Base → Salt + Water
• NH3 is a weak base as it can donate a proton to form NH4+
• Amphoteric substances react with both acids and bases.
• The pH scale measures the concentration of hydronium ions in solution on a logarithmic scale from 0 to 14.
• Ethanoic acid --> CH3COOH
• Ethanoic acid is a weak acid.
• Phosphoric acid --> H3PO4
• Stronger acids have more H+ ions than weaker ones, so they are stronger electrolytes.
• Weak acids only partially dissociate into hydrogen ions (H+) and anions when placed in water.
• A buffer solution resists changes in pH when small amounts of strong acid or alkali are added.
• A strong base completely ionises in water, producing hydroxide ions (OH-) and cations.
• Nitric acid --> HN03
• Nitric acid is a strong acid.
• Sulfuric acid -->H2SO4
• Sulfuric acid is a strong acid.
• Hydrochloric acid --> HCl
• Hydrochloric acid is a strong acid.
• Strong acids release all their hydrogen atoms into solution as H+ ions and completely dissociate in aqueous solution.
• A weak acid only releases a small amount of its available hydrogen atoms into solution as H+ ions and only partially dissociates.
• Only the H atom on the COOH group of ethanoic acid is released as H+.
• Most organic acids are weak acids.
• Acid + Carbonate ----> Salt + Water + Carbon Dioxide
• Acid strength decreases across Period 3 because the size of the halogen increases so there's less attraction between the nucleus and the electron cloud making it easier for the electron pair to be removed from the outer shell.
• Why is it important to use an excess of a base when preparing a salt an acid?

  To make sure the acid is completely neutralised.
• Acid + Metal ----> Salt + Hydrogen

  This is a redox reaction.
• Acid + Metal Oxide ----> Salt + Water

  This is a neutralisation reaction.
• Acid + Metal Hydroxide ----> Salt + Water

  This is a neutralisation reaction.
• Acid + Ammonia ----> Salt

  This is a neutralisation reaction.
• The proton of the acid reacts with the hydroxide of the base to form water.
• The spectator ions which are not involved in the formation of water, form the salt.
• Salts are produced in neutralisation reactions.
• Stronger acids will react more vigorously with metals than weak acids.