Acids and Bases

• An acid is a substance with a pH of less than 7. It forms H+ ions in water
• A base is a substance with a pH greater than 7.
• An alkali is a base that dissolve in water, which splits and forms a OH- ion
• The higher the pH, the less H+ ions there are in a solution, so the less acidic it is
• A pH probe can be used to measure pH electronically. It is placed into a solution and gives the pH number on a digital display.
• A pH probe is more accurate than a universal indicator, however must be set to a pH of 7 and rinsed with deionised water between uses
• The reaction between an acid and a base is called neutralisation
• When an acid and a base react, it produces a salt and a water
• Strong acids are ones which ionise almost completely in water. They tend to have a low pH and released H+ ions
• Weak acids do not ionic fully in a solution. Only some of the acid molecules release H+ ions
• An acid strength is the amount of hydrogen ions it can release in a solution.
• As the concentration of H+ ions increases by a factor of 10, the pH decreases by 1.
• A mixed indicator is universal indicator. A single indicator is methyl orange