Wild Chemistry Ride 11:
Acids, Bases and Alkalis
In this topic we learnt on what acids, bases and alkalis are, and also discovered reactions between acids and other substances, such as metals, carbonates and bases.
Acids
• An acid is a substance that produces hydrogen ions in water
• Acids can be characterised into whether they are strong or weak
• Examples of strong acids include sulfuric acid, sulfurous acid, nitric acid, nitrous acid, hydriochloric acid, phosphoric acid and phosphorous acid
• Examples of weak acids include ethanoic acid (which is commonly found in vinegar) as well as carbonic acid
• Acids dissolve in water to form hydrogen ions, which is why blue litmus paper does not turn red when it comes into contact with, for example, hydrogen chloride. For the blue litmus paper to turn red, the hydrogen chloride must dissolve in water, because in this way hydrogen ions are produced and thus it turns the blue litmus paper red.
• Acids turn blue litmus paper red and universal indicator red/ yellow, showing that their PH is <7
• Metal + Acid --> Salt + Hydrogen gas
^this reaction is indicative of the presence of a reactive metal, and effervescence is produced. The gas evolved extinguishes a lighted split with a pop sound. Non-reactive metals include Silver, Copper and Gold.
• Carbonate + Acid --> Salt + Carbon dioxide + Water
^effervescence is produced. The gas evolved produces a white precipitate in limewater. I learnt from this topic that we should no longer write "the limewater turned chalky", but rather state that "there was a white precipitate produced in the limewater"
Bases
• A base is any metal oxide or hydroxide that reacts with an acid to produce a salt and water only (no effervescence produced)
• Examples of common bases include Copper (II) oxide, Magnesium oxide, Sodium hydroxide
• Base + Acid --> salt + water
Alkali
• An alkali is a type of base that is soluble in water to produce hydroxide ion in water
• Examples of alkalis include sodium hydroxide, potassium hydroxide, aqueous ammonia and calcium hydroxide (otherwise known as limewater and it is slightly soluble)
• Alkalis produce hydroxide ions in water and have a PH greater than 7. Like bases, they turn red litmus blue and universal indicator blue/ violet
Click to watch a video on Acid-Base reaction! :D
Here's a wacky video on sulfuric acid... and sugar!
