Acids, bases and salts Flashcards Preview

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Flashcards in Acids, bases and salts Deck (8)
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1
Q

Describe the characteristic properties of acids as
reactions with metals, bases, carbonates and effect
on litmus

A

Properties:

  • sour tasting, corrosive
  • pH < 7
  • are H+ ion (proton) donors
  • turns litmus red
  • acid + metal oxides/hydroxides -> salt + water
  • acid + metal -> salt + hydrogen
  • acid + carbonates -> salt + water + co2
  • acid + base -> salt +water (neutralisation)
2
Q

Describe the characteristic properties of bases as
reactions with acids and with ammonium salts and
effect on litmus

A

Properties:

  • corrosive, soapy
  • pH > 7
  • proton acceptors
  • turns litmus blue
  • base + ammonium salts -> salt + ammonia + water
3
Q

Describe the meaning of weak and strong

acids and bases

A
Strong acid/base:
- Fully ionised (donate/ accept all protons)
e.g. acid: HCl, H2SO4 (sulphuric), HNO3 (nitric)
        base: NaOH (sodium hydroxide)
Weak acid/base
- Partially ionised
e.g. acid: CH3COOH (ethanoic)
       base: NH3 (ammonia)
4
Q

Classify oxides as either acidic or basic, related to

metallic and non-metallic character. Further classify other oxides as neutral or amphoteric

A
  • Metal oxides are basic. React with acid to form salt and water
  • Most basic oxides do not react with water except for Group I and II metals to form metal hydroxide
  • Non-metal oxides are acidic. Reacts with alkali to form salt and water. Formed direct reaction with oxygen
  • React with water to form acidic solutions
  • Neutral oxides do not react with acids or bases (N20, NO, CO)
  • Amphetoric oxides have both acidic and bases properties and react with both of them
5
Q

Making salts: reacting a metal with acid

A
  • Add metal to acid (metal is in excess)
  • Warm the flask gently
  • Filter off the excess metal. The filtrate is the solution of metal salt
  • Put the filtrate in an evaporating dish and evaporate until crystallisation point is reached. Allow salt to crystallise
  • Filter off the crystals and wash them with tiny amount of distilled water
  • Dry it
6
Q

Making salts: titration method

A
  • Measure the volume of alkali into flask using a volumetric pipette
  • Add few drops of indicator solution to the alkali
  • Fill a burette with acid
  • Record the burette reading
  • Open the burette tap and let acid flow. Swirl to make sure the alkali and acid mixe and react
  • Stop adding when indicator changes colour
  • Record the burette reading. Take final - initial
  • Crystallisation
7
Q

Making salts: precipitation

A
  • Making insoluble salts
  • Done by mixing two soluble compounds (this is a precipitate)
  • Filter off the precipitate
  • Precipitate is washed with distilled water and dried
8
Q

Methods of collecting gas

A
  • Downward displacement is for gas that is lighter than air: hydrogen, ammonia
  • Upward displacement is for gas that is heavier than air: carbon dioxide, chlorine, hydrogen chlorine
  • Downward displacement of water is used for gas that is insoluble in water: hydrogen, oxygen