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Need guide to titrations (1 Viewer)

murder1

New Member
Joined
Jul 25, 2002
Messages
10
Hey

Can anyone here post a complete idiots guide to titrations, the calculations needed, blah blah

any help would be appreciated

ps. my chem prac for the trials will be on a titration
 

SuperNova

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Joined
Jul 7, 2002
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32
Location
Sydney
Mate this is a extract of my notes . not perfect and the calculations r too hard to type up so u gonna need to check out the text books but excel has pretty good questions involving it




Titration
We used anhydrous sodium carbonate as the standard solution and hydrochloric acid as the titre (volume of the liquid delivered).

Equipment:
Volumetric flask, burette, pipette, dropper, conical flask, indicator, a beaker, goggles

Standard solution:
1. Weigh out the solid using a very accurate balance of the calculated mass. Use n=CV to calculate the mass required.
2. Transfer the solid to a volumetric flask (washed with distilled water)
3. Add distilled water until the flask is about half full, swirl to dissolve the solid.
4. Add more distilled water and carefully add the last drops using a dropper until the meniscus is at the calibrated mark.

Preparation:
1. Wash the burette with HCl and the pipette with the standard solution.
2. Remove the air bubbles from the burette before filling it with HCl
3. Pipette 25ml of standard solution into the conical flask (touch the glass with the pipette for the solution to run through but do not blow the last drop as it has already been calibrated in the glassware).
4. Add two drops of indicator into the conical flask

Titration process:
1. Swirl the solution in the conical flask during a titration to ensure good mixing of the tow solutions, but try not to shake it hard enough to mix air into it. (The carbon dioxide in the air dissolve in water and can change the pH)
2. Remember right hand swirl left hand control
3. Repeat the concordant (proper trials not including the first approximate one) titrations at least 3 times
 

bertyboi

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Joined
Aug 5, 2002
Messages
9
Location
Merrylands
Basically the moles = [ ] X Volume formula is the main one your going to be using, how you're going to implement it is depended on how well you know how to substitute and convert to SI units etc.
To determine the concentration of potassium permanganate by titrating oxalic acid
~0.02mol/L Potassium Permanganate and 0.05mol/L Oxalic acid
Titre Permanganate required in Litres
1 0.012
2 0.0115
3 0.0125
Average Potassium Permanganate volume = 0.012
Determining the concentration of potassium permanganate
Moles = [ ] X Volume
Moles = 0.05 X 0.025
Moles = 0.00125 Oxalic Acid
5H2C2O4 + 2MnO4 + 6H 10CO2 + 9H2O + 2Mn
5:2 ratio
0.00125 X 5/2 = 0.003125 moles of potassium permanganate
Moles = [ ] X Volume
0.003125 = [ ] X 0.012
[ ] = 0.2604 mol/L
Ethanol and 0.083mol/L Potassium Permanganate
Titre Permanganate required in Litres
1 0.0325
2 0.0315
3 0.032
Average Potassium Permanganate Volume = 0.032L
Determining the concentration of ethanol in a bottle of VB
Moles = [ ] X Volume
Moles = 0.2604 X 0.032
Moles = 0.00833 Potassium Permanganate
5CH3CH2OH + 4MnO4 + 12H 5CH3COOH + 11H2O + 4Mn
5:4 ratio
0.00833 X 5/4 = 0.0104 moles of ethanol
Moles = [ ] X Volume
0.0104 = [ ] X 0.025
[ ] = 0.416 mol/L
% V/v = 0.0416mol/100mL
% Calculated alcohol = 4.16%
Specified content = 4.9%

this is one concerning the alcohol content in wine/beer in the 3rd module.
 

murder1

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Joined
Jul 25, 2002
Messages
10
Hey thanks guys i did my prac yeasterday and we did the titratoin of orange juice against NaOH to find the molarity and percentage of ascorbic acid :)
 

fillstar

Member
Joined
Aug 10, 2002
Messages
97
Gender
Male
HSC
2002
I done the exact same experiment testing for citiric acid instead. But you're really assuming that all the acids (ascorbic, citric etc.) are reacting with the base and not just a particular acid.

The colour of the juice put our results off though :(
 

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