acids, bases and salts Flashcards
definition of an acid
an acid is a substance which dissociates in water/aqueous solutions to give hydrogen ions. all acids contain H+ ions.
what do pure acid exist as?
simple covalent molecules.
only when does an acid exhibit acid properties?
when dissolved in water -> dissociation -> presence of water.
definition of the basicity of an acid?
basicity of an acid is the maximum number of hydrogen ions produced by one molecule of the acid when the acid molecule dissociates in water.
what are three strong acids?
hydrochloric acid (HCI) sulfuric acid (H2SO4) and nitric acid (HNO3)
what are the two weak acids?
ethanols acids (CH3COOH) and carbonic acids (H2CO3)
what does the strength of an acid depend on?
strength of an acid depends on the extent of dissociation/ionisation of the acid molecules in water/aqueous solution.
a strong acid ______ dissociates in water while a weak acid _____ dissociates in water.
a strong acid completely dissociates in water while a weak acid partially dissociates in water.
what is the concentration of a solution?
the concentration of a solution is a measure of how much solute has dissolved in 1dm3 of the solution.
what is the unit for concentration?
mol/dm3.
what are the four physical properties of acids.
- sour
- turns blue litmus paper red
- pH < 7
- can conduct electricity
chemical properties of acids
they react with reactive metals, metal (hydrogen) carbonates and bases (metal oxides/hydroxides).
what are the soluble salts?
- sodium, potassium, ammonium and group 1 salts
- nitrate salts
- sulfate salts (except Ba, Ca, Pb)
- chloride salts (except Ag, Pb)
- carbonate salts (Na, K2, (NH4)2)
what are some soluble oxides?
Na2O, K2O, BaO, CaO, group 1 metals
what are some soluble hydroxides?
NaOH, KOH, Ba(OH)2, Ca(OH)2, group 1 metals
what are the three non-reactive metals?
Cu, Ag, Au.
acid + metal - > ?
salt + hydrogen.
acid + metal carbonate -> ?
salt + carbon dioxide + water.
what is the chemical formula of limewater?
Ca(OH)2
why is white precipitate seen when carbon dioxide is passed into limewater?
carbon dioxide gas (acidic gas) reacts with limewater (alkali) to give calcium carbonate, an insoluble salt which appears as a white precipitate.
what is a base?
a base is a substance that reacts with an acid to form salt and water only.
what are alkalis?
alkalis are bases that dissociate in water to produce hydroxide ions.
what are the five alkalis we have to know?
- aqueous sodium hydroxide
- aqueous potassium hydroxide
- aqueous calcium hydroxide
- aqueous ammonia
- aqueous barium hydroxide (weak)
a strong alkali _____ dissociates in water to give hydroxide ions
a weak alkali ________ dissociates in water to give hydroxide ions
a strong alkali completely dissociates in water to give hydroxide ions.
a weak alkali partially dissociates in water to give hydroxide ions.
base + acid ->?
salt + water (neutralisation)
alkali + ammonium salt -> ?
salt + ammonia gas + water.
what reaction is used to test for cations?
precipitation reaction.
what happens in the precipitation reaction?
aqueous solution containing metal ions + alkali (metal hydroxide solution) -> insoluble metal hydroxide (precipitate) + salt
what is 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.
the more ____ the solution, the ____ the concentration of hydrogen ions
the more acidic the solution,the higher the concentration of hydrogen ions.
what is an indicator?
an indicator is an organic compound which changes in colour in accordance with the pH of the solution
