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HBSC2103

FACULTY OF EDUCATION AND LANGUAGES

SEMESTER SEPTEMBER / 2012HBSC 2103CHEMISTRY 1MATRICULATION NO: 700908035084001

IDENTITY CARD NO.: 700908035084

TELEPHONE NO.: 019-9542303E-MAIL

: malihanmustafa@yahoo.com.my

LEARNING CENTRE: Petaling Jaya

1.0 INTRODUCTION

Salts play an important role in our daily life.It widely use in food preservation, in agricultures, medicine and other uses.As an example in the agricultures field, nitrate salt such as potassium nitrate ( KNO3 ) , sodium nitrate (NaNO3) )and ammonium salts such as ammonium sulphate ( NH4)3SO42) , ammonia nitrate ( NH4NO3 ) are used as nitrogenous fertelizers .While salts such as copper sulfate ( CuSO4 ) , iron (11) sulphate ( FESO4 ) and mercury chloride ( HgCI ) are used as pesticides.In the medication field , most of the medications are made off salts. Antacid medicine contain calcium carbonate CaCO3 and calcium hydrogen carbonate Ca (HCO3 )2 that are used to reduce acidity in the stomachs of gasrtric patients.Another familiar and popular examples is Panadol or paracetomol which we use to relieve headaches and fever.Plasters of paris , used to support fractured bones, also contain salt , calcium sulphate CaSO4. There are various type of salt occurs in this world such as Sodium chloride NaCl, Copper (II) carbonate CuCO3 and so on. Lead nitrate Pb(NO3)2, lead carbonate PbCO3, potassium nitrate KNO3, and potassium carbonate K2CO3 are several types of them.Salt is a an ionic compound produced when the hydrogen ion H+ from an acid replaced by a metal ion or an ammonium ion, NH4. Salt consist of cations (positive ions) originating from base that combined with anions (negative ions) originating from acids. The cations and the anions of a salt are bonded by strong ionic bond.Not all salts are soluble in water .There are soluble and non soluble salts. Soluble salts are salts that dissolve in water at room temperature while salts that cannot dissolve in water are called insoluble salts .Soluble salts can be prepared in the laboratory by four method .The four method are reaction between an acid and alkali, reaction between acid and metal, reaction between an acid and a metal carbonate and reaction between an acid and metal okside or hydroxide.While insoluble salts can be prepared by precipitation in a double decomposition reaction.In the precipition method , an insoluble salt is precipitated when two aqueous solutions containing the cations and the anions are mixed together.The precipitate is then obtain by filteration.2.0 4 TYPES OF SUBSTANCES.2.1Lead nitrate Pb(NO3)2Lead nitrate also known in IUPAC name as lead (II) nitrate. Lead nitrate is water soluble salt with it solubility in water is about 52g/100mL at 20 Degree Celsius. It forms a colourless solution when dissolved in water. It is also an inorganic compound compose of nitric acid and lead. The chemical formula for lead nitrate is Pb(NO3)2. Normally lead nitrate occurs as colourless crystal, or white powder. Other name for lead nitrate is plumbous nitrate, lead dinitrate, and plumb dulcis. Lead (II) nitrate also known as a toxic salt, harmful and dangerous to environment. Besides that, lead (II) nitrate also is an oxidizing agent, and is categorized as probably carcinogenic to human by International Agency for Research on Cancer. So lead (II) nitrate must be handled and stored with the appropriate safety precautions. It is important to avoid inhalation, ingestion and skin contact. Normally lead (II) nitrate does not occur naturally. It can be obtained by dissolving metallic lead in an aqueous nitric acid.2.2Lead carbonate PbCO3

Lead carbonate composed of lead and carbonic acid. Unlike lead nitrate, lead carbonate is insoluble salt. It solubility in water is about 0.00011g/100mL. It is also known as crussite and become a popular collection of mineral. Molecular formula for this salt is PbCO3. Lead carbonate, PbCO3 occurs as white powder at 20 Degree Celsius and melting at 315 Degree Celsius. Lead carbonate PbCO3 is also insoluble in alcohol but it is soluble in acids and alkaline. Lead carbonate PbCO3 prepared industrially from lead (II) acetate and carbon dioxide by passing carbon dioxide into a cold dilute solution of lead (II) acetate.

2.3Potassium nitrate KNO3Potassium nitrate is also known as saltpeter or nitrate of potash. It is an ionic salt of potassium ions, K+ and nitrate ions, NO3-. The chemical formula for this salt is KNO3 and its molecular mass is about 101.1032g/mol. Potassium nitrate appears in white solid and only melting at 334 Degree Celsius. It is odorless and soluble in water. It solubility in water is about 383g/L at 25 Degree Celsius. It is slightly soluble in ethanol and also soluble in glycerol and ammonia. Potassium nitrate KNO3 is harmful if swallowed, inhaled or absorbed on skin. It will cause irritation to skin and eyes area. Potassium nitrate, KNO3 is highly used in fertilizer, food additive, fireworks and rockets propellants. Combination of ammonium nitrate and potassium hydroxide will produced potassium nitrate. This is shown by the equation: NH4NO3(aq) + KOH (aq) NH3(g) + KNO3(aq) + H2O (l)

ammonium nitrate (aqueous) + potassium hydroxide (aqueous) ammonia(gases)+ potassium nitrate (aqueous) + water (liquid)

2.4Potassium carbonate K2CO3Potassium carbonate is a white salt which is soluble in water but in soluble in alcohol and acetone. When dissolve in water, potassium carbonate will form a strong alkaline solution. Other names for potassium carbonate K2CO3 are potash and pearl ash. Molar mass for potassium carbonate, K2CO3 is about 138.205g/mol with density 2.29g/cm3. The absorbance reaction between potassium hydroxide KOH and carbon dioxide CO2 will produce potassium carbonate, K2CO3. Usually potassium carbonate is used in production of glass and soap. 3.0HOW TO IDENTIFIED AND FIND OUT THE SUBSTANCEThe given substance can be indentified using the Qualitative Analysis. Qualitative analysis is a chemical methods or technique to determine the substances present in a compound through certain chemical test. The cation and anion in salt normally can be identified through: The technique of qualitative analysis includes .i) Colour and solubility of the salt ii) Confirmatory test for anioniii) Confirmatory test for cationiv) Gas testv) Effect of heat on salt 3.1Identified The Colour and Solubility Of The SaltThe colour of the salt can be identified by observation. As the colour of lead nitrate, Pb(NO2)3, lead carbonate, PbCO3 , potassium nitrate, KNO3, and potassium carbonate, K2CO3, are same in colour, it is difficult to differentiate between them. So, the next test is test for the solubility of the salt.The apparatus needed to carry out this test are test tubes, glass rods, spatula and test tube holder.The given substance is put in the test tube using a spatula,Distilled water are added to the above test tube.The mixture is strirred and the solubility of salt is observed. From these four types of salt mention before, only lead carbonate, PbCO3, is insoluble in water.So if the substance is insoluble in the water the substance is lead carbonate, PbCO3. But, if the substance is soluble, the salt must proceed to the other test for identified whether it is potassium carbonate, K2CO3, potassium nitrate, KNO3, or lead nitrate, Pb(NO2)3.3.2Confirmatory Test For AnionAnions that are normally tested in qualitative analysis are carbonate ions CO32, Chloride ions, Cl- , Sulphate ions, SO42, and nitrate ions, NO3. Since, the anion present in potassium nitrate, KNO3, lead nitrate, Pb(NO2)3, and potassium carbonate K2CO3, are nitrate ions and carbonate ions, so the anions test is just for carbonate ion test and nitrate ion test. The apparatus used in this experiment are test tubes, and delivery tube with stopper. Before a chemical test can be performed, the salt needs to be dissolved in water first to produce an aqueous solution. The aqueous solution then divides into two test tubes. The first test tube is used to test the present of carbonate ions CO32-. 3.2.1Carbonate ion test:i. About 2 cm-3 of unidentified salt solution is poured into the test tube. Then, a little dilute hydrochloric acid, HCl, is added into the solution. Gas that produced is passing through lime juice. Lime juice is used to indicate the present of carbon dioxide gases.ii. If the carbonate ions, CO3- present, the effervescence occurs and the gas released by the salt solution will clouds the lime juice.iii. When there is the present of carbonate ions, CO3-, adding hydrochloric acid will produced carbon dioxide gas and water. This is due to the hydrogen ions in hydrochloric acids combine with oxygen from carbonate ions to produced water. The equation is shown below:

CO32-(aq) + 2H+ (aq) C02 (g) + H2O (l)

Carbonate ions (aqoues) + 2 hydrogen ions carbon dioxide (gases) + water (liquid) Figure 1: Carbonate ions CO32- test.

3.2.2Nitrate ions test:

i. About 2 cm3 of unidentified salt solution is poured into a test tubes and about 2cm3 dilute sulphuric acids then added to the solution followed by the addition of 2cm3 of iron(II)sulphate, FeSO4, solution. After that, several drops of concentrated sulphuric acids, H2SO4, are added slowly into the solution. At this time the test tube must be slant and do not shake.ii. If brown ring form, it is shown the present of nitrate ions NO3-. If not, there is absence of nitrate ions NO3- in the solutions.

Nitrate ions test is also known as brown ring test. Addition of the iron(II)sulphate, FeSO4 to a solution of nitrate, and then followed with slowly addition of concentrated sulphuric acids, H2SO4, will form a layer below an aqueous solution. A brown ring is form at the junction of the two layers which indicate the presence of nitrate ions. The overall reaction is shown below:

NO3-+ 3Fe2++ 4H+ 3Fe3++ NO + 2H2O

[Fe(H2O)6]2++ NO [Fe(H2O)5(NO)]2++ H2O

This reaction shows reductionof the nitrate ion by iron (II) which is oxidized to iron(III) and formation of a nitrosonium complex.

Figure 2: Nitrate ions, NO3- test (Brown ring test).So, by using anions test, it can shows whether there is the present of nitrate ions NO3- or carbonate ions CO32- in the unidentified salt solution. If carbonate ions, CO32- , is present, the salt is potassium carbonate. But if nitrate ions NO3-, is present in the unidentified salt solution, it is either potassium nitrate, KNO3, or lead nitrate Pb(NO3)2 . To shows whether it potassium nitrate, KNO3, or lead nitrate, Pb(NO3)2, conformation test for cation must be done.3.3Confirmatory Test For Cation.Normally in solid form, cation can be classified into coloured cation and white cation. The same as test for anions, test for cation also needs the salt to be dissolved in water to form aqueous solution. In an aqueous solution the cation can be divide into two, one is colourless aqueous cation solution and the other one is coloured aqueous cation solutions. Colour blue indicate the present of copper, CU2+, Green for the present of FE2+ and Brown showed the present of Fe3+. For the present of cation such as lead Pb2+ , zinc Zn2+, calcium Ca2+, and so on, the solution is colourless. As in this laboratory test, we have to differentiate between potassium nitrate and lead nitrate, the cation test is just to test the present of lead ions Pb2+.

To test the present of lead ions, test tube and sodium hydroxide NaOH solutions is needed. First, 1cm3 of unidentified salt solution is poured into test tube. Then, sodium hydroxide, NaOH solution is added drop by drop until excess while shaking it. If the present of lead ions Pb2+, the white precipitate is occurs when sodium hydroxide NaOH is added and the white precipitated then soluble in access of sodium hydroxide NaOH. The present of lead ions will shows that the salt is lead nitrate, Pb(NO3)2 but if the salt solutions shows the absent of the lead ions, it is potassium nitrate KNO3.

Figure 3: Test for cation Pb2+3.4Effect of Heat On Nitrate Salt and Carbonate Salt

3.4.1Effect Of Heat On Nitrat

Heating test on salt also can be done to identified either it is nitrate salt or carbonate salt .All ammonium , carbonate , nitrate and some sulphates salts will decomposed when heated.All ammonium salts liberate ammonia gas when heated.All carbonates except potassium carbonate and sodium carbonate produce carbon diokside gas when heated .To test the effet off heat on carbonate salts the exsperimen below can be carried out.Apparatus : Boiling tube, test tube , test tube holder , delivery tube with rubber stopper , spatula and Bunsen burner.

Materials : Potasium carbonate and lead (11) carbonate or an known substance given and lime water.

Prosedure

1. One spatula of substance is placed in dry boiling tube and the colour of solid is recorded.

2. The boiling tube is fitted with a stopper with a delivery tube.

3. The carbonate salt is heated slowly and then strongly.

4. Any gas evolved is passed through the delivery tube into the lime water.The effect of lime water is recorded

5. When there is no further change .The colour of residue when it is hot is recorded.The colour of residue when it is cold to room temperature is also recorded.6. The experiment is set up as shown in figure 4.

Figure 4 Heating test on carbonate salts

Result

Carbonate SaltColour Of Salt before heatingCalour of residueEffect on limewater

When hotWhen cold

Pottassium Caobonate,K2CO3whitewhitewhiteNo visible change

Lead(11) carbonate, PbCO3

whitebrownyellowLimewater turn milky

DiscussionWhen lead carbonate is heated , Lead (11 ) oxide and carbon dioxide gas are produced.

PbCO3(s ) PbO(S) + CO2(g)Lead (11) oxide is brown when hot and yellow when cool

ConclusionPotassium carbonate will not decomposed on heating ,So only Lead(11) carbonate is decomposed to lead (11) okside and carbon dioxide gas which milky the limewater.So the substances are lead (11) carbonate.3.4.2Effect of heat on nitrate saltAll nitrate decomposed when heated. Nitrate salts will produced oxygen gas , nitrogen dioxide gas and metal oksides when heated .To identify the the nitrate substance we can carried out an experiment given below.Apparatus

Boilong tubes, litmus paper , test tube holder, woodent splint , spatula and Bunsen burner

MaterialNitrate salt

Procedure

1. One spatula of nitrate is placed in dry boiling tube and the colour of solid is noted.

2. The boiling tube is fitted with a stopper with a delivery tube.

3. The nitrate salt is heated slowly and then strongly.

4. Any gas evolved is tested by a glowing wooden splint ( Figure 6 a ) and moist blue litmus paper ( Figure 6 b ) .The result are recorded.

5. When there is no further change,.the colour of residue is recorded when it is hot .The colour of residue is recorded again when the residue is cooled to room temperature .If the salts are nitare the result as followed

\

Figure 6(a ) and 6 (b)

Result

SaltColour of salt before heatingColour of residueTest on gas

When

hotWhen

coldColour of gasEffect on glowing wooden splintEffect on moist blue

Litmus paper

Potassium nitrate, KNO3whitewhitewhiteColourlessRekindlesNo Change

Lead Pb(NO3)2.whitebrownyellowbrownRekindlesTurn Red

DiscussionThe brown gas that changed moist blue litmus paper to red is nitrogen dioxside gas.The gas that rekindles a glowing wooden block splint is oxygen gas.ConclusionAll nitrate salt decomposed on heating.Potassium nitrate and plumbum nitrate decomposed to oxygen when heated .If the result as above the substances are nitrate salt

4KNO3(s) 2K2O(s) + 2N2(g) + 5O2(g)

2 Pb(NO3)2(s) 2 PbO (s) + 4 NO2(g) + O2(g)4.0Method To Prepared Lead Carbonate PbCO3Lead carbonate is an insoluble salt. The formula for lead carbonate is PbCO3 and usually this salt is also known as Cerussite. Usually present in colourless or white, also yellow, grey and even blue green. One properties of this salt is it is very soluble in acid or alkali but insoluble in alcohol or ammonia while it solubility in water is about 0.00011g/100Ml at 20 Degree Celsius. This salt can be prepared through precipitation reaction or known as double decomposition reaction. Double decomposition reaction is the reaction normally used to prepare insoluble salt such as lead carbonate PbCO3, lead sulfate PbSO4, lead chloride PbCl2, zinc carbonate ZnCO3, silver chloride AgCl, and so on. This reaction involves the exchange of ions to produce insoluble salt by mixing the aqueous solution that containing the ion of the insoluble salt that to be formed. This reaction can be shown as:A-B + C-D A-C + B-D

So, to produce PbCO3, the soluble salt can be used are lead nitrate Pb(NO3)2 and potassium carbonate KCO3. To produce 1mol of lead carbonate PbCO3, 1 mol of lead nitrate Pb(NO3)2 and 1 mol of potassium carbonate KCO3 needed. This is due to the chemical equation:

Pb(NO3)2 + KCO3 PbCO3 + 2KNO3

The equation shows that 1 mol of lead nitrate Pb(NO3)2 react with 1 mol of potassium carbonate KCO3 will produce 1 mol of lead carbonate PbCO3 and 2 mol of potassium nitrate KNO3. Before started this reaction, the materials needs are 1 mol dm-3 of potassium carbonate KCO3 and 1mol dm-3 lead nitrate Pb(NO3)2. Apparatus used in this laboratory activity are two of 250cm3 beakers, glass rod, filter paper, and filter funnel. Then, 50cm3 of 1mol dm-3 of lead nitrate Pb(NO3)2 is added to the same amount of 1 mol dm-3 of potassium carbonate KCO3 in a beaker. The mixture then stirred by using glass rod for about two or three minutes. After that, leave the mixture for a while, and you will see the precipitated are formed. This precipitated is lead carbonate PbCO3 precipitation.

The next step is filtered the mixture with filtered paper. By using the filter paper, lead carbonate PbCO3 precipitate can be separate from potassium nitrate KNO3 .The salt crystal or lead carbonate precipitation then will stick at the filter paper while the soluble salt potassium nitrate will go through the filter paper. A small amount of distilled water then used to rinse the salt. This is to make sure the access of potassium nitrate KNO3 will be removed from the lead carbonate PbCO3 precipitated. Lead carbonate precipitated then dried under the sunlight or using microwave. The dried lead carbonate then is able to be used.

From this double decomposition reaction, precipitation that occurs between lead nitrate and lead carbonate solution is:

Pb(NO3)2 (aq) + KCO3 (aq) PbCO3 (s) + 2KNO3 (aq)

This precipitated reaction also can be represent in ionic equation as:

Pb2+ (aq) + CO32- (aq) PbCO3 (s)

Lead ion (aqueous solution) + Carbonate ion (aqueous solution) lead carbonate (solid)

Figure 7 : Preparation of insoluble salt lead carbonate PbCO3For the conclusion, PbCO3 can be prepared through double decomposition reaction between lead nitrate Pb(NO3)2 and potassium carbonate KCO3 solutions. Lead ions Pb2+ will combine with carbonate ions CO32- to produce solid lead carbonate PbCO3.

3125 wordsReferences

1. Tok Kheng, Yeap. (2009) Essential Chemistry. Selangor: Pearson Longman.2. Tan Yin Toon, Loh wai and Tan On Tin (2012 ) Success Chemistry SPM.Selangor:Oxford Fajar Sdn Bhd.

3. Dr Tan Juat Ngoh, Dr Asha Kumarai Chunnu Lal and Zulkefli Daud ( 2012 ) HBSC2103 CHEMISTRY 1, Selangor.Meteor Doc.4. http://en.wikipedia.org/wiki/Lead(II)_nitrate5. http://answers.yahoo.com/question/index?qid=20081118002025AAKz0Pp6. http://cameochemicals.noaa.gov/chemical/37427. http://www.gravitaindia.com/leadnitrate.html8. http://en.wikipedia.org/wiki/Lead_carbonate9. http://www.galleries.com/Cerussite10. http://en.wikipedia.org/wiki/Potassium_nitrate11. http://en.wikipedia.org/wiki/Nitrate_testhttp://en.wikipedia.org/wiki/Salt_methathesis Substance

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