Slide 1

Chapter 8 : SALT 2 Types of salt

Soluble Insoluble11Chapter 8 : SALT Table of solubility of salts :

SaltSolubility of salts in waterNitrate salts, NOAll are soluble in waterK , Na and NH saltsAll are soluble in water

Chloride salts , Cl All soluble except AgCl and PbClSulphate salts , SO All soluble except PbSO, BaSO, CaSO

Carbonate salts, COAll insoluble in water except K , Na and NH .2SOLUBLE SALT Na, K or NH Preparation of soluble Na, K or NH salt:Titration method, Neutralisation reaction. Example : HCl + NaOH NaCl + HO3SOLUBLE SALT Na, K or NH Procedure : Titration MethodUse titration method to neutralise acid and alkali.

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Crystallisation Heat the salt solution produced until saturated.Cool at room temperature to allow salt crystals to form.Filter,wash and dry with two pieces of filter paper.

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OTHER SOLUBLE SALTPreparation of other soluble salts :Neutralisation method: (all involved acid)Acid with reactive metalEg : 2HCl + Zn ZnCl + H2) Acid with metal oxide / baseEg : HNO3+ CuO Cu(NO3)2 + HO3) Acid with metal carbonateZn (CO3)2 + HCl ZnCl2 + CO2 + H2O6OTHER SOLUBLE SALTProcedure : Neutralisation method.Excess solid added to hot dilute acid.Unreacted solid is filtered.Filtrate/salt solution is heated until saturated Cool at room temperature until crystals formed.Filter, wash and dry using two filter paper.

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INSOLUBLE SALTDouble Decomposition method :2 soluble salt solution are added to produce precipitate/ insoluble salt.

Eg : Pb(NO) + 2KCl PbCl + 2KNO precipitate8

8Colours of oxidePbO = Brown when hot, Yellow when cold ZnO = Yellow when hot, White when cold CuO = Black Other metal oxide = white9

Effect of heatCarbonates

10K2CO3 & Na2CO3 No RxnOther carbonates will decompose to release CO2 and produce metal oxide.Ex : Al2 (CO3)3 MgCO3Al2 (CO3)3 Al2O3 + 3CO2MgCO3 MgO + CO2

Nitrates11KNO3 & NaNO3 (Only this 2 metal nitrates form metal nitrite and oxygen when heated)KNO3 KNO2 + O2NaNO3 NaNO2 + O2Other nitrates will decompose to form metal oxide and release NO2 & O2 Al(NO3)3 Al2O3 + NO2 + O2Ca(NO3)2 CaO + NO2 + O2

Test for gases12O2Rekindles a glowing wooden splinterH2Gives a pop sound when tested with lighted wooden splinter CO2Turns lime water become milkyColourless gasNH3Pungent smellTurns litmus paper from red to blueForm white fumes with concentrated HClNO2Reddish-Brown colour gasTurn litmus paper from blue to red (acidic gas)Pungent smellHCl - Forms white fumes with concentrated ammonia

SO2 - Decolourised the purple colour of acidified potassium manganate (VII) solution.INSOLUBLE SALTProcedure :Salt solution with cation of insoluble salt mix with another salt solution with anion of insoluble salt.Filter out the precipitate formed.Wash and dry the precipitate.

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SALT ANALYSIS (ANION)

Test for CO : Limewater milky

Use acid with CO Bubbled gas produced into limewaterTurns milky/cloudy1414

SALT ANALYSIS (ANION)

Test for NO : Brown ring test

Add dilute HSO Then add FeSO solutionShake to mix wellAdd concentrated HSO carefully down the side of the test tube.Brown ring observed.1515

SALT ANALYSIS (ANION)

Test for SO : White precipitate

Add dilute HCl.Then add BaCl2 solution.White precipitate obtained.

1616SALT ANALYSIS (ANION)Test for Cl : White precipitate

Add dilute HNO.Then add AgNO solution.White precipitate obtained.

1717SALT ANALYSIS (CATION)Add a little NaOH solution :

No precipitate

NH present1818SALT ANALYSIS (CATION)Add a little NaOH solution :

Coloured Precipitate formed

Blue : Cu presentGreen : Fe presentBrown : Fe present

1919SALT ANALYSIS (CATION)Add a little NaOH solution : White Precipitate formed

Soluble in excess :Zn , Al , Pb (ZAP)

Insoluble in excess : Ca , Mg (CaM)

2020SALT ANALYSIS (CATION)Add a little NHOH solution :

No precipitate

NH present Ca present2121SALT ANALYSIS (CATION)Add a little NHOH solution :

Coloured Precipitate formed

Blue : Cu soluble in excess, dark blue solution producedGreen : Fe presentBrown : Fe present2222SALT ANALYSIS (CATION)Add a little NHOH solution : White Precipitate formedSoluble in excess : Zn only

Insoluble in excess : Mg , Al, Pb (MAP)

2323SPM 2003 : SECTION C ( Q4 )You are required to prepare dry magnesiumchloride salt. The chemicals supplied areMagnesium sulphate solution,Dilute hydrochloric acid,Potassium carbonate solution, Describe a lab laboratory experiment toprepare the salt. In your description, include the chemical equations involved. (10 marks)2424Analyse, Think and Plan Need to use all 3 reagents. Magnesium chloride salt is soluble. 4 methods to prepare soluble salt, use acid with metal carbonate method. So prepare insoluble carbonate salt first. Use double decomposition method. Prepare insoluble MgCO salt using 2 salt solution which is magnesium sulphate solution and potassium carbonate solution.

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Answer

Pour 50 cm of 1.0 mol dm magnesium sulphate solution into a beaker and add 50 cm of 1.0 mol dm potassium carbonate solution.

The mixture is stirred. White precipitate magnesium carbonate formed is filtered, washed and dried between two filter papers.2626AnswerThe chemical equation involved is : MgSO + KCO MgCO + KSOPour 50 cm of 1.0 mol dm of hydrochloric acid into a beaker and heat it.Add the white precipitate, MgCO bit by bit until excess into the hydrochloric acid.Filter the mixture to remove the excess magnesium carbonate.2727AnswerThe chemical equation for the reaction between MgCO and HCl is : MgCO + 2HCl MgCl + HO + COHeat the filtrate, MgCl to saturate it until 1/3 of its original volume.Cool the saturated solution and filter to obtain the crystal magnesium chloride.The crystal magnesium chloride formed is washed with cold distilled water and dried between filter papers.2828SPM 2005 : SECTION B (Q8)Diagram below shows two reagent bottles each containing an aqueous solution.

Hydrochloric acidAmmonium chloride solution2929SPM 2005 : SECTION B (Q8)Qualitative analysis can be used to determinethe presence of cations and anions in solutions.Describe chemical tests that can be used toverify the ions in each solution. (10 marks)3030AnswerHydrochloric acid is poured into a test tube.Dilute nitric acid is added followed by silver nitrate solution.White precipitate formed confirm the presence of chloride ions.31 solution

31AnswerHydrochloric acid is poured into a test tube.Half a spatula of zinc metal is added into the acid and the gas released is tested with a burning wooden splinter.A pop sound verifies the presence of hydrogen ions in the acid.3232AnswerAmmonium chloride solution is poured into a test tube.Sodium hydroxide solution is added and no precipitate formed.When this mixture is heated, a pungent smell released verifies the presence of ammonium ions3333AnswerOr :Ammonium chloride solution is poured into a test tube.Nessler reagent is added and the formation of brown precipitate verifies the presence of ammonium ions.The same test to verify the presence of chloride ion in HCl is carried out to verify chloride ion in ammonium chloride solution.

34Prepared by :

Pn Grace Chin Mei Foong.GC ( Chemistry )SMK St Mary,Kuala Lumpur35