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GCSE Chemistry Notes: Preparing a salt from an acid plus insoluble base or metal
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6b. Making a soluble salt from an acid and an
insoluble base (can be an oxide, hydroxide, carbonate) or metal
Index of all my GCSE notes on acids, bases
GCSE Chemistry Revision
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Index of all my GCSE notes on acids, bases and salts
All my GCSE Chemistry Revision notes
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Method (a) Making a salt by neutralising a soluble acid with a soluble base (alkali) - neutralisation reaction
Method (b) preparing a salt by reacting an acid with a metal or with an insoluble base - oxide, hydroxide or carbonate (this page)
Method (c) Preparing an insoluble salt by mixing solutions of two soluble compounds
Method (d) Making a salt by directly combining its constituent elements
Doc Brown's chemistry revision notes: basic school chemistry science GCSE chemistry, IGCSE chemistry, O level & ~US grades 8, 9, 10 school science courses for ~14-16 year old science students for national examinations in chemistry topics including acids bases alkalis salts preparations reactions
6. METHODS of MAKING SALTS - salt preparation procedures
Salt solubility affects the method you choose to make a salt, the table below will help you decide on the method
One important point is to recognise that one of the reactants is insoluble here, which is why you can't use a titration procedure to work out how much of the acid is to be added to a given amount of the solid. However, you can add the solid reactant to the acid until no more reacts and dissolves and then filter off the excess solid leaving a solution of the desired salt.
6b. A 2nd Method of Making a Water Soluble Salt
6b. METHOD (b) Reacting an acid with a metal or with an insoluble base to give a soluble salt
Typical examples shown by the word and symbol
equations below include ... copper(II) oxide +
sulfuric acid ==> copper(II) sulfate
water CuO +
H2SO4 ==> CuSO4 +
H2O CuO(s) +
H2SO4(aq) ==> CuSO4(aq) +
copper(II) oxide + sulfuric acid ==> copper(II) sulfate + water
CuO + H2SO4 ==> CuSO4 + H2O
CuO(s) + H2SO4(aq) ==> CuSO4(aq) + H2O(l)
magnesium hydroxide + sulfuric acid ==> magnesium sulfate
water Mg(OH)2 +
H2SO4 ==> MgSO4 +
2H2O Mg(OH)2(s) +
H2SO4(aq) ==> MgSO4(aq) +
magnesium hydroxide + sulfuric acid ==> magnesium sulfate + water
Mg(OH)2 + H2SO4 ==> MgSO4 + 2H2O
Mg(OH)2(s) + H2SO4(aq) ==> MgSO4(aq) + 2H2O(l)
magnesium hydroxide + hydrochloric acid ==> magnesium chloride + water
and with sulfuric acid a blue solution of copper(II) sulfate is formed.
copper(II) carbonate + sulfuric acid ==> Copper(II) sulfate + water + carbon dioxide
copper(II) carbonate + nitric acid ==> Copper(II) nitrate + water + carbon dioxide
Similar equations for other carbonates to give soluble salts which can be crystallised from solution e.g.
More examples of neutralization
equations are given in section 4.
METHOD (b) Procedure for making a soluble salt from an insoluble base, carbonate or metal
Don't forget to wear safety glasses or goggles when doing this preparation.
(1) The required volume of acid is measured out into the beaker with a measuring cylinder. The excess of insoluble metal, oxide, hydroxide or carbonate is weighed out (*) and the solid added in small portions to the acid in the beaker with stirring. Doing a weighing will minimise trial and error especially if the reaction is slow, as long as you know how to do the theoretical calculation and add on a little excess!
You need to be able to calculate the quantities required.
(*) You can avoid doing a calculation and weighing of the insoluble solid reactant by adding small quantities to the hot acid until no more apparently dissolves.
(2) The mixture may be heated to speed up the reaction. When no more of the solid dissolves it means ALL the acid is neutralised and there should be a little excess solid.
(3) The hot solution (with care!) is filtered to remove the excess solid metal/oxide/carbonate, into an evaporating dish.
(4) You may need to carefully heat the solution to evaporate some of the water.
Extra guidance notes
Salt solubility affects the method you choose to make a salt and so section 8. contains tables of information-data on salt solubility which will help you decide on the method to prepare a salt.
GCSE/IGCSE Acids & Alkalis revision notes sub–index: Index of all pH, Acids, Alkalis, Salts Notes 1. Examples of everyday acids, alkalis, salts, pH of solution, hazard warning signs : 2. pH scale, indicators, ionic theory of acids–alkali neutralisation : 4. Reactions of acids with metals/oxides/hydroxides/carbonates, neutralisation reactions : 5. Reactions of bases–alkalis like ammonia & sodium hydroxide : 6. Four methods of making salts : 7. Changes in pH in a neutralisation, choice and use of indicators : 8. Important formulae of compounds, salt solubility and water of crystallisation : 10. More on Acid–Base Theory and Weak and Strong Acids
Advanced Level Chemistry Students Acid-Base Revision
Notes - use index
GCSE/IGCSE foundation-easier multiple choice quiz on pH, Indicators, Acids, Bases, Neutralisation and Salts
GCSE/IGCSE higher-harder multiple choice quiz on pH, Indicators, Acids, Bases, Neutralisation and Salts
GCSE/IGCSE Structured question worksheet on Acid Reaction word equations and symbol equation questions
GCSE/IGCSE word-fill worksheet on Acids, Bases, Neutralisation and Salts
See also Advanced Level Chemistry Students Acid-Base Revision Notes - use index
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