Determination of Concentration of Potassium Hydroxide

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Determination of Concentration of Potassium Hydroxide

Weigh boat0.87g
Weigh boat + Sulphamic acid3.29g
Weigh boat after transfer0.87g
Sulphamic acid2.42g

 | Trial| 1st| 2nd| 3rd| 4th| 5th|
Start| 3.00| 3.20| 5.20| 18.55| 1.90| 14.65|
Finish| 17.35| 18.10| 18.10| 31.50| 14.65| 27.65|
Titre| 14.35| 14.90| 14.90| 12.95| 12.75| 13.00|

Average titre = 12.90cm3

NH2SO3H + KOH – NH2SO3K + H20

Sulphamic Acid Standard Solution
Moles from mass weighedMoles = Mass
Mr
= 2.42
97.1
= 0.0249mol
Molarity of solutionConcentration = Moles
Volume
= 0.0249
(250 ÷ 1000)
= 0.0996dm3

Titration
Moles of NH2SO3H Moles = Volume x Concentration
= 12.90 x 0.0996
1000
= 1.28484 X10-3 moles

From equation 1 mole NH2SO3H = 1 mole KOH

Molarity of KOHConcentration = Moles
Volume
= 1.28484 X10-3
0.025
= 0.0514 mol dm-3
Evaluation
Percentage error % Error = Uncertainty x 100
Actual reading

Instrument| Uncertainty| Reading taken| % Error|
Balance(g)| 0.10| 12.90| 0.77|
Burette(cm3)| 0.01| 2.42| 0.41|
Volumetric pipette(cm3)| 0.02| 25.00| 0.08|
Flask(cm3)| 0.10| 250.00| 0.04|

Ensuring accurate results –
* Ensure apparatus is free of contamination by flushing out with liquid to be used or distilled water. * Do trial titration first.
* Repeat titration until concordant results obtained (within 0.1cm3) * At the final stage of titration use the drop method
* Only use a few drops of indicator on each titration.
* Use a piece of paper with a black dot to view the meniscus more clearly
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