chapter 4 - acids, bases and neutralisation

• when dissolved in water, an acid releases hydrogen ions as protons
• a strong acid is an acid hat completely dissociates into H+ ions
• a sea acid is an acid that only partially dissociates into H+ ions
• HCl is a strong acid

  CH3COOH is a weak acid
• a base neutralises an acid to form a salt
• an alkali is a base that dissolves in after releasing hydroxide ions into the solution
• acid + alkali -> salt + water
• acid + carbonate -> salt + water + carbon dioxide
• titrations are used for

  • finding the concentration of a solution
  • identification of unknown chemicals
  • finding the purity of a substance
• preparing a standard solution

  1. the solid is weighed first
  2. solid dissolved in the beaker using less distilled water then can fill the flask
  3. solution is transferred to a volumetric flask, last traces are rinsed by distilled water
  4. flask is filled to graduation line carefully, drop by drop
  5. finally, the volumetric flask is inverted slowly to mix the solution
• uncertainties 


  10 cm3 pipette 0.04

  25 cm3 pipette 0.06

  50 cm3 brunette 0.10
• acid base titration

  1. add a measured volume of acid to conical flask
  2. add alkali to a brunette and record initial reasing
  3. add indicator to conical flask
  4. run solution in brunette for rough
  5. record final burette
  6. repeat more accurately until concordant results are achieved
• concordant results are results within 0.1 cm3 of eachother
• oxidation number is 0 for elements
• sum of the oxidation numbers = total charge
• reduction is the gain of electrons, and decrease in oxidation number
• oxidation is the loss of electrons and the increase of oxidation number
• metal + cid -> salt + hydrogen