acids and bases

• ph scales measures how acidic or alkaline a solution is
• universal indicator is a dye that changes colour depending on the pH of the solution
• an acid is a substance that forms aqueous solutions with ph less than 7
• a base is a solution with a pH above 7.0
• an alkali is a base that dissolves in water to form a solution with a pH above 7
• acids form h+ ions in water
• alkalis form OH- ions in water
• a reaction between an acid and a base is called a neutralisation reaction
• acid + base= salt + water
• H+ + OH- = H20
• when products are neutral they have a ph of 7
• stronger acids produce more h+ ions so their solutions are more acidic
• strong acids ionise completely in water to form hydrogen ions (H+)
• weak acids do not fully ionise so only a small proportion of the acid is dissociated to form H+
• ionisation of weak acid is a reversible reaction so the equilibrium is unstable since only a few acid particles release H+ position lies on left
• for every decrease of 1 on the ph scale, concentration of H+ ions increases by 10x
• an acid with a ph of 4 has 10x concentration of H+ in a ph of 5
• concentration of acid is how much acid is in a given volume of solution