1acids, bases and salt preparations Flashcards
ionic compounds are
generally soluble in water compared to covalent substances, however there are exceptions
soluble ionic compounds
compounds of sodium potassium and ammonia, all nitrates, all chlorides except silver and lead (II), all sulfates except barium, calcium and lead(II), sodium potassium and ammonium carbonates, sodium potassium and calcium hydroxides
insoluble ionic compounds
silver and lead (II), barium calcium and lead (II), all other carbonates except sodium potassium and ammonium carbonates, all hydroxides except sodium potassium and calcium hydroxide
calcium hydroxide is
slightly soluble in water
acids in terms of proton transfer
acids are proton donors as they ionise in solution producing protons, H^+ ions, these H^+ ions make aqueous solution acidic
bases in terms of proton transfer
bases are proton accepters as they ionise in solution producing OH^- ions which can accept protons, these OH^- ions make the aqueous solution alkaline
only metals above
hydrogen in the reactivity series will react with dilute acids
the more reactive a metal is
the mire vigorous the reaction will be
metals that are placed high on the reactivity series are
very dangerous and react explosively with acids
when acids react with metals they form
a salt and hydrogen gas
general equation for a metal and salt and hydrogen gas reaction
metal + acid -> salt + hydrogen
when an acid reacts with a base a
neutralisation reaction occurs
acid base neutralisation equation
acid + base -> salt + water
the identity of a salt produced depends on
the acid used and the positive ions in the base
hydrochloric acid produces
chloride
sulfuric acid produces
sulfate salts
nitric acid produces
nitrates
metal oxides and metal hydroxides act as
bases
acids will react with metal carbonates to form the
corresponding metal salt, carbon dioxide and water
bases are
substances which can neutralise an acid forming salt and water
in alkaline conditions red litmus paper turns
blue
bases are usually
oxides, hydroxides or carbonates of metals
the presence of the OH^- ions is what
makes the aqueous solution an alkali
how to prepare a soluble salt from the reaction of an acid with an insoluble base
During the preparation of soluble salts, the insoluble reactant is added in excess to ensure that all of the acid has reacted
If this step is not completed, any unreacted acid would become dangerously concentrated during evaporation and crystallisation
The excess reactant is then removed by filtration to ensure that only the salt and water remain
Since all of the acid has reacted and the excess solid base has been removed then the solution left can only be salt and water
If a carbonate was used as the solid base instead of an oxide or hydroxide, then any carbon dioxide gas produced would have been released into the atmosphere
A common example is the preparation of copper(II) sulfate which can be made with copper(II) oxide and dilute sulfuric acid:
CuO (s) + H2SO4 (aq) ⟶ CuSO4 (s) + H2O (l)
The acid could also be reacted with a metal to produce the salt, as long as the metal is above hydrogen in the reactivity series and not too reactive so that a dangerous reaction does not take place
materials needed to prepare copper (II) sulfate
1.0 mol / dm3 dilute sulfuric acid Copper(II) oxide Spatula & glass rod Measuring cylinder & 100 cm3 beaker Bunsen burner Tripod, gauze & heatproof mat Filter funnel & paper, conical flask Evaporating basin and dish.
method to prepare copper (II) sulfate
Add 50 cm3 dilute acid into a beaker and warm gently using a Bunsen burner
Add the copper(II) oxide slowly to the hot dilute acid and stir until the base is in excess (i.e. until the base stops dissolving and a suspension of the base forms in the acid)
Filter the mixture into an evaporating basin to remove the excess base
Gently heat the solution in a water bath or with an electric heater to evaporate the water and to make the solution saturated
Check the solution is saturated by dipping a cold glass rod into the solution and seeing if crystals form on the end
Leave the filtrate in a warm place to dry and crystallise
Decant excess solution and allow the crystals to dry
results of preparing copper (II) sulfate
Hydrated copper(II) sulfate crystals should be bright blue and regularly shaped
