Write an essay about the main stream molecular descriptors molecular weight (MW), octanol – water partition P (Log P), hydrogen bond donors (HD), hydrogen bond acceptors (HA), rotatable bonds (RT) and polar surface area (PSA) in the context of drug discovery. See for example: Zhu et al. Mol. Inf., 2012, 31, 847-855.
Minimum: 5 pages
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June 13th 2017
EXPERIMENT 2 – ACID-BASE TITRATIONS, CHEM 240
Titrimetric analysis of polyprotic acids
AIM: The aim of this experiment was to study acid-base titrations using the potentiometric end point detection. First we standardized the sodium hydroxide solution necessary for titrations and determined the content of citrate in a sample of Enerlyte powder for rehydration.
PROCEDURE: The experiment is done by following the procedure given for the EXP. 2: Acid-Base Titrations, CHEM 240.
Batch number: LoTF03L81
Label claim sodium acid citrate 0.53g
Mass Sachet = 5.1268 ± 0.0001 g
Citric acid mass = 0.60739 ± 0.0001 g
Disodium citrate mass = 2.5850 ± 0.0001 g
c(HCl) = 0.1015 mol/L
5mL pipette ± 0.01
10mL pipette ± 0.04
All titrations were performed using autotitrator Metrohm 785 Titrino system. The change of pH is detected by the Metrohm combined glass electrode.
I Strong Acid (HCl) Titration / Standardisation of NaOH titrant
The solution of NaOH is standardized using the standard solution of HCl.( c(HCl) = 0.1015 mol/L). The aliquot of 5.00 mL of HCl standard solution was transferred using a pipette into a titration vessel, diluted with approximately 65 mL of deionized water and titrated using the NaOH solution of unknown concentration.
Table 1: Titration of HCl with NaOH
# pHI pH=7 fixed mL EP mL EP pH
1 2.25 4.897 4.901 7.36
2 2.23 4.927 4.930 7.27
3 2.17 4.942 4.944 7.07
4 2.20 4.937 4.941 7.24
5 2.18 4.931 4.932 7.06
II Titration of citric acid and disodium hydrogen citrate solutions
Citric acid is accurately weighted (about 0.6 g) and dissolved...