Whats in the water we drink?

Hard water
1. Disadvantages
  1. Difficult to form lather with soap
  2. Scum fomshich wastes soap
  3. Scale (a hard crust) forms inside kettles wasting energy
  4. Hot water pipes 'fur up' which can block them completely
2. Advantages
  1. Preffered taste
  2. Calciumin the water is good for strong teeth and bones
  3. Reduces heart illnesses
  4. Good for making beer
  5. Stops poisonous salts dissolving in water
3. What makes it hard?
  1. If the water supply has flowed through chalk or limestone (calcium carbonate) it will be hard
4. The chemistry of scum
  1. Calcium and magnesium ions that cause hard water are not removed when water is purified at the water works, so they're found in tap water
  2. calcium ions from water(soluble) + stearate ions from soap(soluble) = calcium stearate (scum) (insoluble)
Water softening
1. All rain is acidic due to co2 dissolving in water to form a weak solution of carbonic acid
2. Dissolving the rocks
  1. When rain falls onto rocks, this weak acidity sets off the slow chemical reactions that cause chemical weathering
    1. Some of the minerals in igneuos rocks are slowly turned to clay
      1. The weak carbonic acid has a more direct effect on rocks such as limestone that are made of calcium carbonate
        These rocks are slowly dissolved away as soluble calcium hydrogencarbonate froms
3. Limescale problems
  1. As hard water evaporates (or heated) some co2 is lost with the water, and calcium carbonate reforms
    1. Enhanced if heated meaning kettles, hot water pipes etc all suffer from limescale
  2. Can be easily removed by dissolving it in a weak acid
4. Temporary and permanent hardness
  1. By boiling hard water, you can reverse the reaction driving off the co2 and precipitating all of the calcium ions as calcium carbonate.
    1. Temporary hardness
5. Water softening
  1. Bath salts soften the water immediately by precipitating the calcium and magnesium ions in a double decomposition reaction
    1. Sodium carbonate+calcium ions = calcium carbonate+sodium ions
  2. An expensive option is a ion-exchange column
    1. contains sodium ions (provided by common salts) or hydrogen ions, which can swap places with calcium or magnesium ions in the hard water
      1. It can run continuously for a long time, removing the magnesium and calcium ions from the water.
        Dishwashers have this which is why salts is added regularly
        The water that comes out now however contains sodium ions which are not good for heath

Nächster

Whats in the water we drink?

Beschreibung

Zusammenfassung der Ressource

ähnlicher Inhalt

	Erstellt von ryangriscti vor mehr als 10 Jahre