• No products in the cart.

68

Enter a short description of the course.

FREE
TESTS FOR CATIONS,     Wear eye protection
  1. Add dil. NaOH(aq) a few drops at a time until in excess; if no reaction, warm gently
 
Orange soln. turns yellowWhite ppt. soluble in xs, forming colourless soln.White ppt. insoluble in xsWhite ppt. rapidly turns brown, insoluble in xsRed-brown ppt. insoluble in xsGrey-brown ppt. insoluble in xsBlue-green ppt. soluble in xs giving dark green soln.Dirty green ppt. insoluble in xs, rapidly turns brownGreen ppt. insoluble in xs (no change on heating)Blue soln. gives blue ppt. insol. in xs (black on heating)Pink soln. gives light blue ppt. insoluble in xs(may go pink on heating/standing)On warming, pungent alkaline gas; dense fumes with conc. HCl¨2 immiscible layers/oily drops, disappear on warming Cr2O72- forms CrO42-Zn2+, Al3+, Pb2+, Sn2+, Sn4+Ca2+, Mg2+, Ba2+Mn2+Fe3+Ag+Cr3+Fe2+Ni2+Cu2+ forms Cu(OH)2 then CuOCo2+ NH4+ Ester being hydrolysed
 2NaOHTypical reaction:  Zn2+ (aq) +  2OH-(aq)    →  Zn(OH)2(s)    →    Na2Zn(OH)4(aq) 
  1. Add dil. NH3(aq) a few drops at a time until in excess
 
Orange soln. turns yellowWhite ppt. soluble in xs, forming colourless soln.White ppt. insoluble in xsWhite ppt. rapidly turns brown, insoluble in xsRed-brown ppt. insoluble in xsNo ppt./ brown ppt. rapidly dissolves → colourless soln.Green ppt. insoluble in xsDirty green ppt. insoluble in xs, rapidly turns brownGreen ppt. soluble in xs giving blue soln.Blue soln. gives blue ppt. soluble in xs. → deep blue soln.Pink soln. gives dirty blue ppt. soluble in xs giving yellow-brown (red?) soln.Cr2O72- forms CrO42-Zn2+Al3+, Pb2+, Sn2+, Sn4+Mn2+Fe3+Ag+Cr3+Fe2+Ni2+Cu2+ Co2+ 
 4NH3(aq)Typical reaction:  Zn2+ (aq) +  2OH-(aq)    →  Zn(OH)2(s)    →    Zn(NH3)42+(aq)  +  2OH-(aq)Other common soluble complex is Ag(NH3)2+(aq) 
  1. Add Na2CO3(aq)
 Most of the coloured ppts. will form as in 1 and 2, also:
White ppt.White ppt. darkens on warmingWhite ppt. and colourless gas (CO2)¨brisk evolution of CO2Zn2+, Pb2+, Ca2+, Mg2+, Ba2+Ag+Al3+ ( also Sn2+, Sn4+)Carboxylic acid, or RCOO- or most phenols 
 
  1. Add KI(aq)
 
Yellow ppt. soluble on warming, reforms on cooling(→crystals if cooled slowly)Red-brown soln. maybe with grey solid Blue soln. gives white suspension in red-brown soln.       If Na2S2O3(aq) added white suspension of CuI formsPb2+ forming PbI2 Oxidising agent present, converts I- to I2Cu2+  
 
  1. Add K2CrO4(aq)
 
Yellow soln. goes orangeRed ppt.Bright yellow ppt.Pale yellow ppt.H+Ag+Pb2+ Ba2+
 Typical reaction:  Pb2+ (aq) +  2CrO42-(aq)    →  PbCrO4(s)¨ Organic ions may come in Inorganic section, not ester or phenol but reaction worth knowing!TESTS FOR ANIONS,         Wear eye protection
  1. Add dil. HCl(aq) to solid or soln., warm gently
 
Yellow soln. turns orangeCO2 evolvedSO2 evolvedSO2 evolved and yellow S suspension(H2S evolvedBlue soln. and colourless NO→brown NO2 gas¨Smell of vinegar(White ppt. in cold, colourless soln. hotWhite ppt. becoming grey in lightCrO42- forms Cr2O72-CO32-, HCO3-SO32-S2O32-S2-)NO2-CH3COO-Pb2+, forming PbCl2Ag+, forming AgCl) 
 
  1. Add dil. H2SO4 to solid or soln., warm gently
 Reactions of anions are as above, but note 
(White ppt.Pb2+, Ca2+, Ba2+
 
  1. Add conc. H2SO4 dropwise with care until in xs., warm   SAFETY SPECS!
 Most of the same anion reactions as with dil. will occur, but note: 
HCl evolvedHBr, Br2 and SO2 evolvedHI, I2 and H2S evolvedColourless HNO3(l) evolved then brown NO2 gas(Water evolved and solids change colour,                 e.g. blue → white or green → white¨Gas evolved, burns with blue flame (CO)¨CO and CO2 evolvedCl-Br-I-NO3-Salt is dehydrated)+ve ion indicatedHCOO-C2O42-
 
  1. Add dil. lead nitrate or ethanoate soln.
White, cream/yellow ppt. soluble on warmingWhite ppt. insoluble in dil. HNO3White ppt. soluble in dil. HNO3 → CO2Bright yellow ppt.Cl-, Br-, I-SO42-CO32-CrO42-  or Cr2O72-
 ¨ Organic anions can come in Inorganic qualitative sectionQUALITATIVE ORGANIC ANALYSIS,         Wear goggles, beware of fire
No.TestObservationDeduction
1.AppearanceSolid  LiquidAromatic acid, e.g. benzoic; amide; salt of organic acid or base (if coloured, cation is transition metal)Alcohol; aldehyde; ketone; aliphatic carboxylic acid; ester; amine
2.BurnYellow non sooty flameYellow-orange sooty flameAliphaticAromatic
3.Water plus litmusMiscible and neutralMiscible and acidicSlightly sol., weakly acidicMiscible and alkalineSlightly sol., weakly alkalineSoluble hot, insoluble cold, acidicAlcohol; aldehyde; ketone; esterAcid or salt of amine e.g. C6H5NH3+Cl-PhenolAmine or salt of acid e.g. CH3COO-Na+Aromatic amine e.g. C6H5NH2Aromatic acid e.g. C6H5COOH
4.Na2CO3 or NaHCO3(s) or (aq)Effervescence, CO2[1] evolvedCarboxylic acidPhenols do NOT react
5.NaOH(aq)NH3 evolved in coldNH3 evolved on warmingDissolves (but was insol. in cold water)Fruity smell disappears on warmingNH4+ or RNH3+AmideAromatic acid or phenol Ester hydrolysedto alcohol and salt of acid
6.K2Cr2O7 (aq) +dil.H2SO4;warmOrange soln. goes greenReducing agent e.g. 1° or 2° alcohol; aldehyde; HCOOH or ion
7.Brady’s reagentYellow or orange ppt.Aldehyde or ketone
8.NaHSO3(aq)White ppt. forms slowlyAldehyde or ketone
9.Fehling’s soln., warmBrick red ppt.Aldehyde or reducing agent eg red. sugarKetones do NOT react
10.Tollen’s reagent, warmSilver mirror(may go black but not form mirror)Aldehyde or reducing agentKetones do NOT reactVery clean test tube essential
11.KMnO4(aq)+dil.H2SO4;warmPurple soln. goes colourlessReducing agent; 1° or 2° alcohol; aldehyde; HCOOH or ion, H2C2O4 or ion; alkene
12.Iodoform test: dil. NaOH+xs.I2warmYellow ppt. with antiseptic smellAlcohol with  CH3CH(OH) or aldehyde/ketone with CH3C=ONB addition of fresh Jik followed by xs KI(aq) may give better results
13.Neutral FeCl3(aq)Intense purple colorationRed-brown soln. →brown ppt. on warmingBuff ppt.(on warming)PhenolCarboxylic acid or carboxylate Aromatic acid
  
14.Bromine waterRed/brown→colourless soln.Red/brown→colourless soln. +white ppt.Alkene/unsaturated Phenol; aromatic amine 
15.Anhydrous ZnCl2 in conc. HClInstant white ppt./colorationWhite ppt./coloration in 5minsNo white ppt./coloration3° alcohol2° alcohol 1° alcohol
16.Small piece of Na; DRYEffervescence H2 evolved-OH
17.PCl5; DRYFumes of HCl-OH
18.Soda lime, heatColourless flammable gasDecarboxylation of carboxylic acidNon sooty: aliphaticSooty: aromatic
19.Conc.H2SO4 +alcohol or carboxylic acid; warmSweet smelling vapour SAFETY SPECS!Esterification showing carboxylic acid or alcohol, depending on added reagent
20.Conc.H2SO4Or Al2O3; heatFlammable gas evolvedSAFETY SPECS!Alcohol forming alkene
21.NaNO2(aq) + dil. HCl(aq)-----------------------≤5°C + 2-naphthol or phenolColourless N2 gasYellow oil  Orange/yellow dye1° amine2° amine  Aromatic amine eg C6H5NH2
 [1] Tests for all these gases must be known

Course Currilcum

Yaaka Digital Network ©, a Ultimate Multimedia Consult product