Chapter 8 Flashcards
Describe the characteristic properties of acids as reactions with metals, bases, carbonates and effect on litmus and methyl orange
Acids turn litmus paper red and turns methyl orange red [also turns phenolphthalein colourless and UIP red or orange/yellow depending on the pH]
Acid reacts with metals (above hydrogen in the reactivity series) to form salt + hydrogen, they react with carbonates to form salts + carbon dioxide + water, they also react with bases to form salt + water and ammonia to form ammonium salt.
Acidic oxides can be produced from a non-metal + oxygen
acids
proton (hydrogen ion) donor; Acids are substances which produce hydrogen ions in solution
bases
proton (hydrogen ion) acceptor; bases are substances that produce hydroxide ions in solution.
Describe neutrality and relative acidity and alkalinity in terms of pH measured using universal indicator paper
If the colour is yellow-green, the substance has the pH 7 and is neutral. If it is yellow to orange, the pH can be 6-3 making it a weak acid. If it is red, it can be 3-1 making it a strong acid. If it is green to blue, it can have a pH of 8-10, making it a weak alkali. If it is purple it can be 11-14 making it a strong alkali
Describe and explain the importance of controlling acidity in soil
If the soil is too acidic, the ions in the soil become soluble and therefore can be washed away. This is a problem for plants who needs those ions.
Describe the meaning of weak and strong acids and bases
Strong acids become fully ionised in aqueous solution, weak acids become partially ionised in aqueous solution. Strong bases are fully ionised or dissociated in aqueous solution and weak bases are partially ionised in aqueous solution.
Further classify other oxides as neutral or amphoteric
there are some oxides that show neither basic nor acidic properties. These are known as neutral oxides, like carbon monoxide, dinitrogen oxide and nitrous oxide. Some oxides are amphoteric . This means that they can act as an acid or a base. Examples are aluminium oxide, and zinc(II) oxide
Demonstrate knowledge and understanding of preparation, separation and purification of salts
An insoluble base reacts with an acid to form a salt. To get the salt:
- add excess base to the acid
- use filter paper and funnel to remove any more unreacted base
- keep in warm place to evaporate water, salt crystals left behind.
An soluble base reacts with an acid and forms a soluble salt.
- use acid/base tritiation to find the exact volume of base needed to neutralise an acid with phenolphthalein.
- Redo the experiment without the phenolphthalein and collect the solution made. leave in a warm place for water to evaporate and collect the salt crystals via an evaporating dish.
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Demonstrate knowledge and understanding of the preparation of insoluble salts by precipitation
Preparation of insoluble salts and soluble salts:
- Mix equal quantities of the two soluble salts.
- Filter to remove the insoluble salt or precipitate. (The soluble salt goes through the filter paper and is known as the filtrate .)
- Wash the precipitate with water.
- Leave to dry.
Suggest a method of making a given salt from a suitable starting material, given appropriate information
Preparation of soluble salts:
1. An acid + metal (excluding sodium and potassium as they are too reactive and copper, silver and gold as they will not react with metals)
2. An acid + metal oxide (insoluble base)
3. An acid + metal carbonate
4. An acid + metal hydroxide (soluble base or alkali).
If the salt is insoluble then you should use a precipitation reaction.**
Describe the following tests to identify aqueous cations
Cation - aqueous sodium hydroxide - aqueous ammonia
aluminium - White ppt., soluble in excess, gives a colourless solution - White ppt., insoluble in excess
calcium - White ppt., insoluble in excess - No ppt., or very slightly white ppt.
chromium(III) - Green ppt., soluble in excess - gives a green solution - Grey-green ppt., soluble to some extent in excess - gives blue solution
copper(II) - Light blue ppt., insoluble in excess - Light blue ppt., soluble in excess – gives a dark blue solution
iron(II) - Green ppt., insoluble in excess - Green ppt., insoluble in excess
iron(III) - Red-brown ppt., insoluble in excess - Red-brown ppt., insoluble in excess
zinc - White ppt., soluble in excess – gives a colourless solution - White ppt., soluble in excess – gives a colourless solution
Describe the following tests to identify cations
Flame test: lithium - Red sodium - yellow potassium - lilac copper(II) - blue-green
Describe the following tests to identify anions
carbonate - add dilute acid - carbon dioxide produced
chloride - Acidify with dilute nitric acid, then add aqueous silver nitrate - White ppt.
bromide - Acidify with dilute nitric acid, then add aqueous silver nitrate - Cream ppt.
iodide - Acidify with dilute nitric acid, then add aqueous silver nitrate - Yellow ppt.
nitrate - Add aqueous sodium hydroxide then aluminium foil; warm carefully - ammonia produced (damp litmus paper red)
sulfate - Acidify, then add aqueous barium nitrate or barium chloride - White ppt.
sulfite - Add dilute hydrochloric acid, warm gently and test for the presence of sulfur dioxide - Sulfur dioxide produced will turn acidified aqueous potassium manganate(VII) from purple to colourless.
Describe the following tests to identify gases
ammonia -Turns damp red litmus paper blue
carbon dioxide - Turns limewater milky
chlorine - Bleaches damp litmus paper
hydrogen - ‘Pops’ with a lighted splint
oxygen - Relights a glowing splint
sulfur dioxide - Turns acidified aqueous potassium manganate(VII) from purple to colourless
Describe the characteristic properties of bases as reactions with acids and with ammonium salts and effect on litmus and methyl orange
Bases turn litmus paper blue and methyl orange yellow [ turns phenolphthalein pink and UIP strong- purple and weak-blue]
Bases react with ammonium salts to form ammonia + salt + water. They react with acids in the same way as described in flashcard 1
