Acids and Bases & Oxides Flashcards
What is an acid?
A substance that dissolves in water to give H+ ions (as the only positive ions)
What is the difference between a strong and weak acid?
A strong acid completely ionises in water to give H+ ions
eg. H2SO4 (stronger as more H+ ion), HCl, HNO3
A weak acid partially ionises in water to give H+ ions
eg. H2CO3, CH3COOH
What are the characteristics of acids?
Acid only displays its properties when dissolved in water (H+ ions give it their properties)
1. Tastes sour
2. Corrosive if concentrated
3. pH< 7
4. Turns damp blue litmus paper red
5. Dissolves in water to form solutions which conducts electricity (due to free moving electrons)
What are the 3 reactions with acids?
Acid + metal -> salt + hydrogen
Acid + metal carbonate -> salt + water + carbon dioxide
Acid + alkali -> salt + water
What are the uses of sulfuric acid?
- Manufacture of detergents
- Manufacture of fertilisers (ammonium sulfate)
- Battery acid
Hydrochloric acid used for cleaning impurities
Ethanoic acid used in vinegar
Phosphoric acid used in F&B for sour taste
What is a an alkali/base
An alkali is a substance that dissolves in water to give OH- ions (as the only negative ions), Alkalis are soluble bases
Bases are oxides and hydroxides of metals that react with acids to produce salts and water
What is the difference between a strong and weak alkali?
A strong alkali completely ionises in water to give OH- ions
eg. KOH, NaOH, LiOH
A weak alkali partially ionises in water to produce OH- ions
eg. NH3
What are the characteristics of an alkali?
When a base dissolves in water, it forms an alkali
1. Tastes bitter
2. Soapy feeling
3. Corrosive if concentrated
4. pH >7
5. Turns damp blue litmus paper red
6. Dissolves in water to form solutions that which conduct electricity due to free moving ions
What 3 reactions with alkali
Alkali + ammonium salt -> salt + water + ammonium salt
Alkali + metal salt -> insoluble metal hydroxide + soluble salt
Alkali + acid -> salt + water
What is added to control pH of soil?
To treat acidity,
Calcium oxide (quicklime) OR
Calcium hydroxide (slaked lime) is added
What are the different oxides?
Metal Oxides:
Basic Oxides
- Metal oxide that reacts with ACIDS only to form salt and water,
- eg. Na2O, MgO, CaO, CuO
Amphoteric Oxides
- Metal oxide that reacts with BOTH acids and alkalis to form salt and water
- eg. ZAP
Non-metal Oxides
Acidic Oxides
- Non-metal oxide that reacts with water to produce acids, reacts with ALKALIS only to form salt and water
- eg. CO2, SO2, SiO2,
Neutral Oxides
- Non-metal oxide that reacts with neither acid or base
- eg. CO, NO, H2O
Why slaked lime Ca(OH)² isn’t added to ammonium fertiliser?
Calcium hydroxide reacts with ammonium salt fertilisers to produce ammonia & water.
Nitrogen in ammonia is needed for healthy plant growth escapes to surroundings
