Bases Flashcards
Define base
A base is a substance that reacts with an acid to form a salt and water only
Define alkali
Alkalis are bases that dissociate in water to produce hydroxide ions, OH-
Define strong alkali
A strong alkali completely dissociates in water to give hydroxide ions
What are physical properties of alkali
Bitter, soapy, turns red litmus paper blue, can conduct electricity
Reaction between alkali and ammonium salt
Alkali + Ammonium salt –> salt+ ammonia gas + water
What are observations when ammonium salt is warmed with alkali
Colourless and pungent gas is produced. Gas turns moist red litmus paper blue, gas is ammonia
Why does moist red litmus paper turn blue when ammonia gas is in contact with it
Ammonia dissociates in water to produce hydroxide ions which turn red litmus paper blue
State the reaction that occurs during precipitation using base
Solution containing metal ion + alkali –> insoluble metal hydroxide +salt
Define precipitation
Precipitation is a chemical reaction between which an insoluble product is formed when two aqueous solutions are mixed
What happens during neutralisation between acid and an alkali
Acid + Alkali –> Salt + Water
Define pH
pH is a measure of acidity or alkalinity in aqueous solution
What does pH measure
pH measures the concentration of hydrogen ions in the aqueous solution and is numbered between 0 to 14.
Name three strongly acidic substances
hydrochloric acid, nitric acid, sulfuric acid
Name three weakly acidic substances
Carbonic acid, ethanoic acid, phosphuric acid
Name a neutral substance
Water/aqueous sodium chloride
Name three weakly alkaline substances
Aqueous sodium carbonate, aqueous sodium bicarbonate, aqueous ammonia
Name two strongly alkaline substances
Aqueous sodium hydroxide, aqueous potassium hydroxide
Define an indicator
An indicator is an organic compound which changes colour in accordance with the pH of the solution
What are two advantages of using a pH meter over indicators
More reliable and accurate, can be used in data logging to record rapid changes in pH
Why should a farmer not add calcium hydroxide and ammonium nitrate into the soil at the same time for his plants?
Slaked lime will react with ammonium nitrate to produce ammonia gas which will escape into the air. This will result in the loss of nitrogen content from the fertiliser to the soil
Properties of acidic oxides
- are oxides of non-metals
- usually dissolve and react with water to produce acids
- react with alkalis
Properties of basic oxides
- oxides of metals
- if soluble, dissolve and react with water to produce alkalis
- react with acids
Properties of amphoteric oxides
- are oxides of metals
- do not dissolve in water
- can behave as acidic oxides or basic oxides
Properties of neutral oxides
- oxides of non-metals
- do not dissolve in water
- do not react with acids or alkalis
Name 4 acidic oxides
sulfur dioxide, carbon dioxide, nitrogen dioxide, phosphorus(V) oxide
State type of oxide of dinitrogen monoxide and nitrogen monoxide
Neutral oxides
