dissolve then add 1.0 g MgCl26H2O crystals. Mix to dissolve the crystals. NOTE: The dissolution of Na2H2EDTA∙2H2O may be slow so addition of NaOH pellets while stirring may be added until the solution is clear. Heating the solution may also increase the dissolution of Na2H2EDTA∙2H2O. c. Quantitatively transfer the solution into a 500-mL volumetric flask. Rinse the beaker thrice with small portions of distilled water and transfer the rinse to the volumetric flask. Dilute to mark with distilled water, cover and mix.
Pls compute how to prepare the following solutions:
1. 500.0 mL 0.1000 M stock EDTA solution
a. Weigh an appropriate amount of Na2H2EDTA2H2O (FW=372.24) to the nearest 0.1 mg and transfer
to a 400-mL beaker.
b. Add about 200 mL distilled water. Stir to dissolve then add 1.0 g MgCl26H2O crystals. Mix to
dissolve the crystals.
NOTE: The dissolution of Na2H2EDTA∙2H2O may be slow so addition of NaOH pellets while stirring
may be added until the solution is clear. Heating the solution may also increase the dissolution of
Na2H2EDTA∙2H2O.
c. Quantitatively transfer the solution into a 500-mL volumetric flask. Rinse the beaker thrice with
small portions of distilled water and transfer the rinse to the volumetric flask. Dilute to mark with
distilled water, cover and mix.
d. Transfer to a clean and dry reagent bottle. Label as 0.1000 M stock EDTA solution.
2. 100.0 mL 0.0500 M stock Ca2+ solution
a. Weigh appropriate amount of pure CaCO3 (FW=100.09) to the nearest 0.1 mg into a 250 mL beaker.
Add about 40.0 mL distilled water. Take note of the purity of CaCO3 used.
b. Carefully and slowly add concentrated HCl to dissolve the CaCO3 solids while stirring and heating
the solution in a hotplate. Do this until the CaCO3 solids are completely dissolved or until no more
effervescence is observed.
NOTE: The stirring must be vigorous enough to dissolve the solids. It is advisable to swirl the beaker
using a crucible tong instead of using a stirring rod.
c. Quantitatively transfer the solution into a 100-mL volumetric flask. Dilute to mark with distilled
water, cover and mix.
d. Transfer to a clean, plastic (polyethylene) bottle. Label as 0.0500 M stock Ca2+ solution.
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