titrations

Acid Base TitrationsKeith Warne

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Titration Calculations. (COOH)2.2H2O

Unknown Base (NaOH)OXALIC ACID STANDARD SOLUTION

cb = .. mol.dm-3(COOH)2.2H2O + 2NaOH --> Na2(COO)2 + 4H2O?Concentration and volume known accurately!nvC =


Standard SolutionA standard solution is one for which the concentration is precisely known.Sincec = ................/.................. = .................

Needed:The number of moles of solute (from ...............)The volume of solution.

These values must be accurately determined. Mass is determined accurately using an electronic balance.1.60gsoluteVolume is measured using a Volumetric flask.250 cm3100 cm3 200 cm3 250 cm3


Weighing TechniqueProcedure - Weighing by difference............... scales and clean the pan.Weigh the weighing .................... Add (................................) the required amount of salt. Take care not to drop any salt onto the pan.Transfer the salt to a ................. beaker................................. the weighing container.......................... the final mass of the container from the mass of salt and container to give the mass of salt transferred to the beaker. Mass is determined accurately using an balance (electronic or triple beam).Possible accuracies of 0.1 - 0.0001gResults: Mass salt + container: Final Mass container: Mass salt transferred:


Making a standard solution. Rinse a clean & dry 100 cm3 beaker with a little distilled water.Transfer the correctly weighed amount of salt to the beaker. ........................... .............................................................Add distilled water to the salt and stir gently with a glass rod until all salt is dissolved. DO NOT REMOVE THE ROD FROM THE SOLUTION NOR ALLOW ANY DROPS OF SOLUTION TO .........................................Add ALL the solution to a volumetric flask via funnel. Ensure glass rod and beaker are thoroughly rinsed. (Include ...................................) Add enough solvent to bring the level ..........................................gsolute


Making a standard solution. Use a dropper to bring the level up to the mark.The BOTTOM of the meniscus must .................. .......................... THE LINE of the flask.The flask should then be ........................ at least ........ times to ensure thorough mixing.The bottom of the meniscus must JUST touch the line!!!250 cm3Drag here


Titration Proceedure. ACID STANDARD SOLUTIONunknown BASERinse# the burette with distilled ................and then with small quantities of the ............................................solution.Fill the burette with the standard ......................solution.Take the ...................reading. Does not have to be ..............Rinse # a clean conical flask with .........................................Rinse # a clean pipette with the .................................solution.Pippette 25cm3 of the ...............................solution into the conical flask.Add 3-5 drops of a suitable .......................to the conical flask.Titrate the acid against the base until the FIRST ..................................................COLOUR CHANGE.Note down the volume of acid and repeat this procedure with a fresh conical flask until ...................................RESULTS are obtained. ~0.1 cm3.


Titration Calculations. ACID STANDARD SOLUTIONa ACID + b BASE salt + water AT THE END POINTmoles ............moles ............=............unknown BASE......................=........25cm3 = 0.025dm3C(mol.dm-3)V (dm-3)


Conc of acid = ? x (trying to find)Volume of acid

burette = ......................Molar ratio from ........................... reaction a = acid coefficient (2) b = base coef. (1)(1)Na2 CO3 + 2 HCl 2NaCl + H2O + CO2Conc of base= your

..................... soln. Worked out.Vol. of base= ........................ (25cm3)Solve for xTitration Calculations


Titration Calculations. (COOH)2.2H2O

Unknown Base (NaOH)OXALIC ACID STANDARD SOLUTION

cb = .. mol.dm-3(COOH)2.2H2O + 2NaOH --> Na2(COO)2 + 4H2O?Concentration and volume known accurately!nvC =CaVaCbVb=ab


Titration Calculations. (COO)2.2H2O Mr = (2(12+32+1)+2(18)= 1266.4g in 1l (1dm3)Moles(ACID) = m/Mr= 6.4/(126) = 0.05mol/1dm3Concentration (ACID) = 0.05 M

Unknown Base (NaOH)

OXALIC ACID STANDARD SOLUTIONAT THE END POINT(1)(COO)2.2H2O + 2NaOH --> Na2(COO)2 + 4H2OOne mole of acid reacts with 2 moles of base..: n(acid) : n(base) 1 : 2CaVaCbVb=12


Titration ExampleIf 22.3 cm-3 of a standard hydrochloric acid solution (0.15 M) was required to reach end point with 25 cm-3 of an unknown sodium carbonate solution, what is the concentration of the sodium carbonate solution? 2HCl + Na2CO3 2NaCl + CO2 + H2O

CaVaCbVb=12(0.15) (0.0223)Cb (0.025)12=Cb= = 0.268 M2*(0.15) (0.0223)1* (0.025)



Nameof indicator Colour acidColour basepH rangeMethyl OrangeRedYellow 3 - 4Bromothymol BlueYellowBlue6 - 8PhenolphthaleinClearRed8 - 10


pH0....Amount of ............ added...


The end point has a pH lower than 7 because the SALT of a STRONG acid and a weak base is ACIDIC!!WEAK BASESTRONG ACIDEND POINTSTRONG ACID WEAK BASE






STRONG BASE WEAK ACIDStrong acid/strong base ..................................Strong acid/weak base ..................................Weak acid/strong base ..................................pH014Moles of base added7Strong acidWeak acidWeak baseStrong baseBlueBromothymol blue

YellowMethyl OrangeRedPinkPhenolphthalienColourlessSTRONG BASE STRONG ACIDWEAK BASE STRONG ACIDSAMPLE ONLYSAMPLE ONLY SAMPLE ONLYFor FULL presentation click HERE >> ScienceCafe


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mass of salt

mass salt container

sample onlyfor

volume of solution

final mass container

drops of solution

cm3 beaker

weighing container