Pure Chem Notes 2023

CHEMPRACTICAL01-Acid An acid is a substance which produces ions in aqueous Solution. Strong𝐻 + Acids completelyioniseinwater togivehighconcentrationof ionsinaqueous𝐻 + solution. Weak acids partially ioniseinwater togivelowconcentrationof ions𝐻 + inaqueoussolution CommonAcids Name Formula Strength HydrochloricAcid 𝐻𝐶𝑙 Strong SulfuricAcid 𝐻₂𝑆𝑂₄ Strong NitricAcid 𝐻𝑁𝑂₃ Strong EthanoicAcid 𝐶𝐻₃𝐶𝑂𝑂𝐻 Weak Properties- Sour Taste- pHlessthan7- Turnsbluelitmuspaper redChemical Reactions- Acid+base→salt +water (neutralisation)- Acid+metal →salt +H ₂ gas- Acid+carbonate→salt +water +CO ₂ gasTest For Gases Gas Test Result Hydrogen Lightedsplint Extinguishwith‘pop’sound CarbonDioxide Limewater Whiteppt

BaseAbaseisasubstancewhichreactswithacidtoproducesalt andwater only.● Basesincludemetal oxides, metal hydroxidesandaqueousammonia● Basescanbesolubleor insolubleinwater● AlkalisaresolublebasesAlkaliAn alkali is a substance which produces ions in aqueous solution. Strong𝑂𝐻⁻ٰalkalis completely ionise in water to give high concentrations of inanaqueous𝑂𝐻⁻ٰsolution. Weak alkalis partially ionise to give low concentrations of in aqueous𝑂𝐻⁻ٰsolutions.CommonAlkalis Name Formula Strength Sodiumhydroxide 𝑁𝑎𝑂𝐻 Strong Potassiumhydroxide 𝐾𝑂𝐻 Strong Calciumhydroxide 𝐶𝑎(𝑂𝐻)₂ Weak Aqueousammonia 𝑁𝐻₃ Weak Properties- Bitter taste- pHmorethan7- Turnsredlitmuspaper blueChemical reactions- Base/ Alkali +acid→salt +water (neutralisation)- Alkali +ammoniumsalt →salt +water + gas𝑁𝐻₃ Test for gas Gas Test Result Ammonia Dampredlitmuspaper Turnsblue

SaltSolubility Salt Preparation Solubilityof Salt Method Separationtechnique Soluble Titration Crystallisation Acid+excessinsolublesolid(base, metal,carbonate) Filtration, thencrystallisation Insoluble Precipitation Filtration SamplePlanningQns:1. Plananexperiment topreparecleandrycrystalsof sodiumchloride2. Describe a suitable method to prepare a clean dry sample of bariumsulfate3. Outline the steps to determine the water of crystallisation in a sample ofhydratedcopper (II) sulfate

SAMPLE:Xcanbeusedtomakelead(II)sulfate.StartingfromX, describeamethodthat canbeusedtomakeapure, drysampleoflead(II)sulfate.Youaregivenasolutionof lead(II) nitrate. Youcanassumethat all theapparatusandreagentsnormallyfoundinaschool laboratoryareavailable. [5] Precipitationoflead(II)nitrate1. Addanexcessofaqueoussilver nitratetoX.Thought Process: Excess silver nitrate needed to precipitate as much chloride as possible. Silver chloridewill be formed. Silver chloride is insoluble. Aqueous bariumnitrate should not beusedasinsolublebariumsulfatewill beformed. 2. Filter themixture.Thought Process: Residueissilver chloride, filtratecontainssilver ions, sulfateionsandnitrateions. 3. Keepthefiltrate.4. Addanexcessofaqueouslead(II)nitratetothefiltrate.Thought Process Insoluble lead (II) sulfate will beformed. Theremainingsolutioncontainssilver ions, lead(II)ionsandnitrateions. 5. Filter themixture.6. Keeptheresidue.Thought Process Residue is lead (II) sulfate, filtrate contai