Acids, bases, and salts

• Two most commonly used indicators are litmus and methyl orange.
• Litmus paper is purple in neutral solutions.
• Alkalis turn litmus paper blue.
• Acids turn litmus paper red.
• Acids are red in methyl orange.
• Alkalis are yellow in methyl orange.
• Acids have a pH less than 7.
• Neutral substances have a pH of 7.
• Alkalis have a pH greater than 7.
• Acids contain excess of H+ ions.
• Alkalia contain an excess of OH- ions.
• Neutral oxides do not react with acids or alkalis.
• Non-metals form acidic oxides.
• Metals form alkali oxides.
• Amphoteric: a hydroxide or metal oxide that reacts with both an acid and an alkali to give a slat and water.
• Amphoteric oxide examples: ZnO and Al2O3
• Soil with minerals such as iron compounds, rotting vegetation, and lack of oxygen, tend to be acid.
• Soils in limestone or chalky areas are alkaline.
• Plants grow best in certain acidities.
• If soil is too acidic, lime can be added.
• If the soil is too alkaline, adding compost and manure can help.
• The soil pH is affected by the use of fertilizers and acidity of rainfall.
• Acid + base --> salt + water
• Alkali is a base that is soluble in water.
• Salt: a compound made from an acid when a metal takes the place od the hydrogen in the acid.
• Metal + acid --> salt + hydrogen
• Acid + metal carbonate --> salt + water + carbon dioxide
• Ammonia gas turns damp red litmus paper blue
• Method of separating salts:

  An excess of the solid is added to the acid and allowed to react, which makes sure that the acid is used up

  The excess solid is filtered out

  The filtrate is evaporated to concentrate the salt solution, which is done on a heated water bath

  When crystals can be seen forming, heating is stopped and solution is left to crystallize