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Posts posted by Borek

  1. Try.


    I don't see why not, I believe around 200 deg C is enough to dry it. I can be wrong though.


    Note: if it absorbed enough water it will melt first (actually it will not melt, but it will dissolve in its own hydration water). You may have to wait several hours before it dries out.


    Question is if you need it perfectly dry, could be partial drying will be enough to make it possible to prepare a powder.

  2. See water ion product to check how water dissociation constant changes with temperature.


    In general no ion can facilitate water dissociation, however, if you dissolve an inert salt increasing ionic strength of the solution, you will observe changes in the water dissociation. But this effect is universal, it is not limitied just to water dissociation. See ionic strength and activity coefficients lecture for details.

  3. You must find out how to convert molarity to molality. Correct conversion formula will contain density and molar mass - you have to solve for density. Check out these concentration lectures for hints on converting (read about %ww to molarity conversions for general outline).


    Strange thing is that 1.0000M solution of KCl is 1.0312 molal. Looks like the data in question are questionable.




    Chemical calculators at www.chembuddy.com

    concentration conversion calculator

  4. Suppose I would want to make 100 ml of a 0.1 M solution of I2. I would weigh 1/3 of 0.01 mol of KIO3 on a glass watch glass. I would rinse this into a beaker of 100 ml. I would take somewhere around 60 ml of water, would add 10 ml of 20% H2SO4 and dissolve all. By rinsing the weighing glass, all iodate is taken into solution, and there is no real loss. To this, I would add 0.15 mol of KI (large excess, enough to make I2 and also keep this in solution as tri-iodide)


    Next, the 70 to 80 ml or so of the liquid is transferred to a volumetric flask of 100 ml. This is an important point, where there can be losses. I would take 10 ml of water, swirl this around in the original beaker and add this to the volumetric glass. A second swirl with 5 ml of water takes the final traces, and then the volumetric flask is filled up to 100 ml. In this way, the transfer losses really are neglicible, and still there is the advantage of not having to deal with (uncertain) side reactions.


    I would rather go with iodate solution prepared from solid directly in the volumetric flask, filling up to the mark. Then I would transfer exactly known volume of iodate to baker and I would add iodide and acid there, avoiding all steps that can introduce error to the iodine amount :)


    When titrating iodine you usually start with yellowish solution - and you don't add starch till solution loses almost all color.




    General Chemistry Software


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