* KS4 Science GCSE/IGCSE Chemistry Notes on 6. Methods of making salts at Doc Brown's Chemistry
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Doc Brown's Chemistry The pH scale of acidity and alkalinity, acids, alkalis, salts and neutralisation 6. Methods of making salts Revision Notes KS4 Science IGCSE/O level/GCSE Chemistry Information Study Notes for revising for AQA GCSE Science, Edexcel 360Science/IGCSE Chemistry & OCR 21stC Science, OCR Gateway Science (revise courses equal to US grades 9-10) Advanced Level Chemistry Acid-Base Revision Notes - use index GCSE Sub-index: Index of all pH, Acids, Alkalis, Salts Notes 1. Examples of acid-alkali chemistry : 2. pH scale, indicators, ionic theory of acids-alkali neutralisation : 3. pH examples of acid, neutral or alkaline solutions : 4. Acid reactions with metals/oxides/hydroxides/carbonates and neutralisation reactions : 5. Reactions of bases-alkalis like sodium hydroxide : 6. Four methods of making salts : 7. Changes in pH in a neutralisation : 8. Important formulae, salt solubility and water of crystallisation : 9. Further examples of word/symbol equations for salt preparations : 10. More on Acid-Base Theory and Weak and Strong Acids 6. METHODS of MAKING SALTS - salt preparation procedures 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. 6a-b. Two Methods of making Salts which are water soluble
Examples of neutralisation equations are given in section 4. Typical common soluble bases (alkalis) used for preparing soluble salts: NaOH sodium hydroxide, KOH potassium hydroxide, NH3 ammonia (1) A known volume of acid is pipetted into a conical flask and universal indicator added. The acid is titrated with the alkali from the burette. (2) The acid is added until the indicator turns green, pH 7 neutral. This means all the acid has been neutralised to form the salt (3) The volume of alkali needed for neutralisation is then noted, this is called the endpoint volume. (1)-(3) are repeated with both known volumes mixed together BUT without the contaminating universal indicator. (4) The solution is transferred to an evaporating dish and heated to partially evaporate the water causing crystallisation or can be left to slowly evaporate - which tends to give bigger and better crystals. (5) The residual liquid can be decanted away and the crystals can be carefully collected and dried by 'dabbing' with a filter paper OR the crystals can be collected by filtration (below) and dried (as above). Note (i) You can put the acid in the burette and the alkali in the flask. (ii) Parts (1) to (3) are known specifically as an acid-base (alkali) titration, and the general method is known as a volumetric titration by which it possible to find out exactly what volume ratios are needed for neutralisation. So knowing one concentration, you can calculate the other. (iii) Concentration calculations are on calculations pages sections 11. and 12. (iv) Apparatus used: (1) pipette and conical flask; (2)-(3) burette and conical flask; (4) evaporating (crystallising) dish, bunsen burner, tripod and gauze; (5) filter paper. (v) Other indicators e.g. phenolphthalein can be used instead (pink alkaline, colourless acid). (vi) The burette and pipette are both used for the accurate measurement of volume. (vii) The pH changes in this preparation are described in section 7. 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.
Examples of neutralization equations are given in section 4. Typical common insoluble bases used for preparing soluble salts: MgO magnesium oxide, MgCO3 magnesium carbonate CaO Calcium oxide, CaCO3 calcium carbonate, Ca(OH)2 calcium hydroxide, NiO nickel(II) oxide, ZnO zinc oxide, Zn(OH)2, zinc hydroxide, ZnCO3 zinc carbonate (1) The required volume of acid is measured out into the beaker with a measuring cylinder. The insoluble metal, oxide, hydroxide or carbonate is weighed out and the solid added in small portions to the acid in the beaker with stirring. (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) The hot solution is left to cool and crystallise. Then collect and dry the crystals with a filter paper. Note (i) Apparatus used: (1) balance, measuring cylinder, beaker and glass stirring rod. (2) beaker/rod, bunsen burner, tripod and gauze; (3)-(4) filter funnel and filter paper, evaporating (crystallising) dish. (ii) A measuring cylinder is adequate for measuring the acid volume, you do not need the accuracy of a pipette or burette required in method (a). (iii) How to calculate amounts required and % yield is dealt with in Chemical Calculations Part 14. 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. Method 6c. Preparing an Insoluble Salt
Method 6d. Making a salt by direct combination of elements
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| La escala del pH de la acidez y la alcalinidad, ácidos, álcalis, sales y neutralización 6. 6. Methods of making salts Los métodos de toma de sales (spanish) * (indonesian) Kimia Skala pH keasaman dan alkalinitas, asam, alkali, garam dan netralisasi Metode pembuatan garam METODE dari PEMBUATAN GARAM - garam prosedur persiapan kelarutan Salt mempengaruhi metode yang Anda memilih untuk membuat garam dan jadi bagian tabel berisi informasi-data kelarutan garam yang akan membantu Anda memutuskan metode untuk mempersiapkan garam. 6a-b. Dua Metode pembuatan Garam yang larut dalam air * |
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