bases

• Base


  A substance which contains oxide or hydroxide ions and reacts with an acid to form a salt and water
• Alkali


  A substance which dissolves in water to produce hydroxide ions as the only negative ions
• Physical properties of bases/alkalis

  • Colourless solutions
  • Bitter taste
  • Corrosive
  • Slippery to touch
  • Can conduct electricity
  • pH value greater than 7
  • Red litmus paper turns blue
  • Blue litmus paper does not change
• Chemical properties of bases/alkalis

  1. Acid+alkali → salt + water

  2. Alkali + ammonium salt→ salt + water + ammonium gas
• Test for ammonium gas

  It is an alkali gas and therefore it turns red litmus paper blue and has no affect on blue litmus paper. It has a sharp odur.
• Classification of alkalis based on strength

  • Strong alkalis (e.g. NaOH, KOH) are completely ionized in aqueous solutions
  • Weak alkalis only a few are ionized in an aqueous solution
• Neutralization reaction


  The reaction between an acid and a base/alkali where water is a product, and the point of neutralisation is where all the acid has reacted with all the alkali
• Acid-base titration


  Used to determine the neutralisation point of an acid-base reaction
• Indicators


  • Litmus (red in acid, blue in base)
  • Phenolphthalein (colourless in acid, pink in base)
  • Methyl orange (red in acid, yellow in base)
  • Screened methyl orange (red in acid, green in base)
  • Bromothymol blue (yellow in acid, blue in base)
• Neutral solutions have a pH value of 7.
• A base is any substance that can accept hydrogen (H+) ions from another compound.
• The pH scale measures the acidity or alkalinity of a solution on a logarithmic scale, with values ranging from 0 to 14.
• A strong acid will produce more H+ than a weak acid when dissolved in water.
• An acid that produces less H+ than another acid when both acids are dissolved in water is weaker than the other acid.
• An acid is any substance that releases H+ ions into a solution when dissolved.
• pH scale measures how acidic or basic a solution is.
• When an acid reacts with a metal carbonate or hydrogen carbonate, carbon dioxide is produced as well as salt and water.
• The pH of a neutral solution is 7
• Acidic substances have a pH below 7
• Weak acids only partially ionize in water, while strong acids completely ionize in water.
• Strong acids completely ionize in an aqueous solution, while weak acids only partially ionize.