Back Titration

BACK TITRATION
AIM - To estimate volumetrically the amount of calcium carbonate present in the eggshell and analyzing the sources of errors to evaluate the result.

Part A: Standardization of 2M NaOH(aq)

Data Collection :
Weight of substances Uncertainty
Weight of watch glass + salt (potassium hydrogen phthalate) w1= 23.4380g ± 0.001g
Weight of watch glass ( after emptying the salt)w2 = 21.5430g ± 0.001g

Weight of salt (potassium hydrogen phthalate) w1 –w2= (23.4380± 0.001g) – (21.5430g ± .001g) = 1.8950± 0.002g

Titration Table -
Volume of distilled water Burette Reading NaOH/ml Volume of NaOH solution for neutralization End point of titration -
50ml Initial final = final - initial Colorless to pale pink 0.0ml± 0.05ml 5.6ml ± 0.05ml = 5.6 ml ± 0.05ml

Data Processing:
Determination of the concentration of NaOH(aq)
Equation: C6H4COOH.COOK + NAOH → C6H4COOK.COONa Ratio of Reactants: 1 : 1
1 mole of Potassium Hydrogen Phthalate (C6H4COOH.COOK) reacts with 1 mole of Sodium Hydroxide (NAOH).
Concentration of NaOH = Weight of Potassium Hydrogen Phthalate Volume of NaOH (dm3) × Molar Mass of Potassium Hydrogen Phthalate 1.8950g ± 0.002g = 1.657 ± 0.017 mol/dm3 0.0056dm3 ± 0.00005dm3 × 204.23g /mole
Concentration of NaOH = 1.657 ± 0.017 mol/dm3

Part B : Standardization of 2M HCl

Data Collection :
Volume of HCl in a conical flask (ml) ± 0.05ml Burette Reading of NaOH(ml) ± 0.05ml Volume of NaOH solution for neutralization End point of titration -
10ml ± 0.05ml Initial final = final – initial = (10.3 ± 0.05ml) – (0.0 ml ± 0.05) Colorless to pale pink
= 0.01 dm3 ±0.00005 dm3 0.0 ml ± 0.05ml