Acids & Bases

Acids & Bases

• 1.
  Acids & Bases
• 2.
  Our Goals fortoday  To determine the difference between Acids & Bases  To describe the characteristic reactions of acids with metals, bases (including alkalis) and carbonates  To describe and explain the importance of controlling acidity in the environment (air, water, and soil)  To perform an experiment dealing with Acids & Bases
• 3.
  What is thepH scale?  The pH scale measures how acidic or basic a solution is.
• 4.
  Identifying Acids andBases Acidshave a pH from 0-7 Lower pH value indicates a stronger acid. Bases have a pH from 7-14 Higher pH value indicates a stronger base.
• 5.
  Definitions of Acidsand Bases  An acid is a substance that breaks into [H+] ions in an aqueous solution.  A Base (alkaline) is a substance that breaks into [OH–] ions in an aqueous solution.  Note: aqueous solution is any solution where H2O is the solvent.
• 6.
  Properties of Acids Taste sour  pH < 7  Acids affect indicators:  Acids turn blue litmus to red  Acids turn methyl orange to red  Acids neutralize bases producing a salt and water  Acids react with active metals to produce hydrogen  Acids react with carbonates to produce a salt, water and CO2  Proton donors (Proton = H+ = hydrogen ion)
• 7.
  The Reactions ofAcids 1. With Bases 2. With Alkali sulphuric acid + copper(II) oxide  copper(II) sulphate + water H2SO4 (aq) + CuO (s)  CuSO4 (aq) + H2O (l) Acid + metal oxide  metal salt + water sulphuric acid + magnesium hydroxide  magnesium sulphate + water H2SO4 (aq) + Mg(OH)2 (aq)  MgSO4 (aq) + 2 H2O (l) Acid + metal hydroxide  metal salt + water
• 8.
  The Reactions ofAcids 3. With Metals Other examples: sulphuric acid + magnesium  magnesium sulphate + hydrogen H2SO4 (aq) + mg (s)  MgSO4 (aq) + H2 (g) Acid + metal  metal salt + hydrogen
• 9.
  The Reactions ofAcids 4. With Carbonates Other examples: hydrochloric acid + calcium carbonate  calcium chloride + water + carbon dioxide 2 HCl (aq) + CaCO3 (s)  CaCl2 (aq) + H2O (l) + CO2 (g) Acid + metal carbonate  metal salt + water + carbon dioxide
• 10.
  Properties of Bases Taste bitter  pH > 7  Bases affect indicators:  Acids turn red litmus to blue  Acids turn methyl orange to  Bases neutralize acids producing a salt and water  Proton acceptors (Proton = H+ = hydrogen ion)  It feels slippery
• 11.
  Neutralization Reaction  Exothermic:it gives out heat  temp. of sol. ↑  Neutralization with ammonia A solution of ammonia in water is alkaline. NH3 + H20  NH4 + + OH– OH– + H+ of acid  Complete neutralization reaction: use indicator PHENOLPHTHALEIN Alkaline Neutral
• 12.
  Everyday Life  Soil:plants will grow best with the pH close to 7. ⁞ Otherwise, we will lack of plant products (vegetables, fruits, nuts, beans, etc) to eat. ⁞ It disturbs ecosystem of the river. ⁞ Quicklime (calcium oxide), Slaked lime (calcium hydroxide), limestone (calcium carbonate)  Water: factory waste. Liquid waste (often acid) reaches rivers. ⁞ It kills fish and other living things. ⁞ It disturbs ecosystem of the river. ⁞ Slaked lime (calcium hydroxide)
• 13.
  Everyday Life  Air:acid rain.  Waste gases from our daily activities (such as gases from our electricity, gases from our transportations, burns from the factory) go into the air.  Carbon dioxide + water from the rainfall  carbonic acid CO2 (g) + H2O (l)  H2CO3 (aq)  Sulphur dioxide and oxides of nitrogen sulphur dioxide + Air + Water  Sulphuric acid oxides of nitrogen  Nitric acid
• 14.
  Everyday Life  Air:acid rain. ⁞ It destroys:  buildings, concrete, cement (calcium carbonate)  Bridges, iron railings, car bodies  Plants ⁞ It dissolves aluminium from minerals in rocks and soil. ⁞ It carries it into the river ⁞ < fish ⁞ Slaked lime (calcium hydroxide)
• 15.
  Did we Misssomething??  What happens when the pH of a substance is 7?  Ans: A pH level of 7 indicates a Neutral Substance i.e: Water! What else besides water?