mayfieldtm
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Can someone check my math?
What is the final Volume of a KOH solution when I add 1300g of KOH flakes into 1 L of water.?
So the volume of the KOH = 1300g/2.044 (density of KOH) = 636.0 cubic cm.
Add 1L of H2O = 1000 + 636.0 = 1636 ml total.
Tom M.
[Edited on 20-3-2012 by mayfieldtm]
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kavu
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You can't do the calculation that way. In solid KOH species are arranged in a lattice, taking up much more space than they would otherwise. Once you
dissolve the KOH it will dissociate to K⁺ and OH⁻ ions. Those ions will be solvated by the water. Depending on the ion strength,
temperature and so forth the total volume gain will differ. I'm not sure if the 1636 mL would be a rough estimate or not. You should also note that
the solubility of KOH in 20°C water is 1210 g.
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woelen
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In most cases it is true that if you mix a volume A of a certain compound with a volume B of another compound that the total volume is less than A +
B. There are few exceptions. But the exact volume of a mix of two compounds is not easily computed. These normally are derived experimentally and
tabulated. You need to find a table of the density of a solution of KOH in water with the density as function of mass percentage. Probably you also
need a table for temperatures higher than 20 C.
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mayfieldtm
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Thanks Kavu and Woelen!
I measured the final volume and indeed it's less than what I calculated. What was I thinking!
It's OK cause I have an excuse... I'm old and decrepit.
I'll look it up.
OH Yes! 1300g is too much. This morning I discovered nice big crystals in the bottom of my Beaker. (room temp 11c)
I'll add water to bring it to about 1200g/L.
It's not a critical solution, it's just an electrolyte for a battery.
However... I'm having fun rediscovering chemistry and exploring the properties such as Volume, PH, Specific Gravity and such.
Tom M.
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