Acids and Bases Notes
- Water (H2O) is a covalent compound of hydrogen and oxygen.
- Randomly and spontaneously, a water molecule will naturally break apart (disassociate) into one H+ and one OH- ion.
- On average, one out of every 555 million H2O molecules will disassociate.
- These ions will soon spontaneously recombine only to be replaced by another H2O disassociating.
- This process is on going and is at equilibrium (balanced).
- We measure the number of H+ ions with the power Hydrogen scale (pH).
- The pH scale ranges from 0 to 14. The lower the number, the higher the number of H+ ions present.
- If we are balanced (same number of H+ and OH- ions) the pH = 7.0
- Pure water has a pH = 7.0
- An acid produces H+ ions when dissolved in water.
- Acids increase the number of H+ ions, the pH reading will go down.
- With a strong acid most of the molecules come apart (disassociate) to form H+ ions.
- In a weak acid only a few molecules disassociate.
- Acids have a sour taste.
Examples of common acids:
- milk = 6.4
- tomato juice = 4.8
- 'pure' rain = 5.6
- stomach acid < 3
- worst acid rain = 1.8
- battery acid = 1.5
- A base produces OH- ions when dissolved in water. The pH will rise.
- With a strong base most of the molecules come apart (disassociate) to form OH- ions.
- In a weak base only a few molecules disassociate.
- Bases have a bitter taste and feel slippery (makes soaps with your skin oils).
Examples of common bases:
- human blood = 7.4
- sea water = 7.8
- ammonia = 11.9
- lye = 13