Determine the atomic weight of covalent metal M. When 4g. of its hydroxide (MOH) are dissolved per dm3 in the given solution, 0.1M HCL is given.
Principle
It is an acid-base titration because MOH is a base which can be use against an acid.
Equation. MOH + HCL → MCl + H2O
Mole ratio. 1: 1
Standard solution. 0.1M HCl.
Indicator. Phenolphthalein.
End point. Just disappearance of pink color.
Procedure:
Take the given solution mixture in the burette and run out some solution through the tip to remove air bubbles. Then note the initial reading. Pipette out 10cm3.of 0.1M Na OH in a nitration flask, add one drop of phenomenological indicator Add HCl from the burette till pink color just disappears. Note the reading. Take three concordant readings.
Observation.
M1 = Polarity of MOH =?
V1 = volume of MOH taken = 10cm3
M2 = Molarity of H Cl = 0.1M
| Sr. NO. |
Initial reading | Final reading | Volume of acid used |
| 1 2 3 |
0.0 12.0 24.0 |
10.0 22.0 34.0 |
10.0cm3 10.0cm3 10.0cm3 |
Mean volume used = 100cm3
Calculations.
MOH HCL
Polarity of MOH = 0.1M
Amount dissolved per dm3 of solution = 4 g.
Amount dissolved per dm3 = Molarity Mo.wt. Of MOH
Mol.wt. of MOH = = 40
Mol.wt. of MOH = Atomic.wt. Of M + Mo.wt. Of OH
= 40 – 17
Result. At.wt. of M = 23
