Determination of Concentration of Potassium Hydroxide

Determination of Concentration of Potassium Hydroxide

Weigh boat 0.87g
Weigh boat + Sulphamic acid 3.29g
Weigh boat after transfer 0.87g
Sulphamic acid 2.42g

| 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 weighed Moles = Mass Mr = 2.42 97.1 = 0.0249mol
Molarity of solution Concentration = 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 KOH Concentration = 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