Chemistry, 8: Acids, bases, and salts

Cards (70)

  • An aqueous solution is formed when a substance dissolves in water
    It can be acidic, alkaline, or neutral
  • A neutral solution is neither acidic or alkaline
  • Red litmus papers show acidic solutions
  • Blue litmus paper shows alkaline solution
  • Phenolphthalein indicator is colourless in acid, but pink in alkaline solutions
  • Methyl orange is pink in acid, but yellow in alkaline solution.
  • Acids are substances that contains replaceable hydrogen atoms
    They can be replaced by metal atoms to form salts
  • Acids have a pH of 0-6
  • What are some common acids?
    Hydrochloric acid, HCl
    Nitric acid, HNO3
    Sulfuric acid, H2SO4
    Phosphorous acid, H3PO4
  • Acidic properties are only seen when water is present
    In water, acids form hydrogen ions
    H+ ions create this acidic properties
  • Acids are proton donors
    E.g.
    HCl -> H+ + Cl-
  • What happens when an acid and metal reacts?
    Makes salt and hydrogen gas
  • What happens when an acid and carbonate reacts?
    Makes salt, carbon dioxide, and water
  • What happens when an acid and base reacts?

    Makes salt and water
  • Bases are oxides and hydroxides of metals
  • Alkalis form when oxides or hydroxides of a metal dissolves in water
    E.g. sodium + oxygen -> sodium oxide
    sodium oxide + water -> sodium hydroxide
  • Sodium oxide is a base because it is the oxide of sodium
    It reacts with water to make alkali sodium hydroxide
  • What happens when a base and acid reacts?
    Forms salt and water
  • What happens when a base and ammonium compound reacts?
    Forms ammonia gas
  • Alkalis only show alkaline properties in presence of water
    In water, alkalis form OH- ions
    These OH- ions reacts with H+ ions from acid to make water
  • Alkalis are proton acceptors
  • If soil is too acidic, it can be neutralised with quicklime
  • Quicklime is made from limestone
    It is heated in lime kilns at 1200°C to make calcium oxide
    When it is added to water, it makes calcium hydroxide, an alkali that neutralizes the soil
  • Oxides of elements are made by heating it in air or oxygen
  • Basic oxides that dissolves in water are alkalis
  • Oxides that do not dissolve in water can be identified using pH
    Or tested to react with:
    HCl, a basic oxide
    NaOH, acidic oxide
    If they do not react with either they are neutral oxides
  • Most metals are basic oxides
    Basic oxides react with acids
    Acid + base -> salt + water
  • Most non-metal oxides are acidic
    Acidic oxides react with bases (neutralisee) and dissolves in water to form acid
  • Metal oxides react with acids to make salt + water
  • Non-metal oxides react with base to make salt + water
  • Amphoteric oxides are oxides of less reactive metals
    They behave as both acid and basic oxides
  • Neutral oxides do not react with acids or bases
  • Acids contain replaceable hydrogen atoms which is replaced by metal to form a salt
  • What are common acids and salts?
    HCl, Cl-
    HNO3, NO3-
    H2SO4, SO4^2-
    H3PO4, PO4^3-
  • Salts are ionic compounds which are found in the form of crystals
  • Salts that don’t contain water are anhydrous
  • All common sodium, potassium, and ammonium salts are soluble
  • All nitrates are soluble
  • Common chlorides, bromides, and iodides are soluble
    Excluding silver chloride, silver bromide, and silver iodide
  • Common sulfates are soluble
    Except barium, lead, and calcium