How can I prepare 100 mM CaCl2 solution?How many gram Cacl2 should I weight and add to distilled water?

Question

How can I prepare 100 mM CaCl2 solution?How many gram Cacl2 should I weight and add to distilled water?

Answer 1

It depends what sort of solid CaCl2 you have (anhydrous, or partially hydrated).

The Mol. Mass of the different forms are:

CaCl2 - 110.99

CaCl2.2H2O (Dihydrate) - 147.02

CaCl2.4H2O (Tetrahydrate) - 183.04

CaCl2.6H2O (Hexahydrate) - 219.08

To make a 1M solution, you would weigh that amount and dissolve it in 1 litre of distilled water.

To make a 100mM colution (a 0.1M solution), you weigh 1/10 that amount, and dissolve in 1L of distilled water.

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aequalst and Howard V are correct, of course.

You should dissolve the relevant amount in a smaller volume, and then make it up to 1L total volume (because the salts will change the volume of the liquid when added to it).

Answer 2

100 mM = 100 mmoles / L so to make one liter of solution you need 100 millimoles of CaCl2.

100 mmoles CaCl2 x (1 mole / 1000 mmoles) x (110.9 g CaCl2 / 1 mole CaCl2) = 11.09 g CaCl2.

So dissolve 11.09 g of ANHYDROUS CaCl2 with a little water, dilute to a final volume of 1L, and mix well.

Be sure that the CaCl2 is anhydrous. If you happen to have CaCl2 x 2H2O instead, then weigh 14.69 g to take into account the water in the crystal structure.

Answer 3

Howard V is correct.

Griblin has given the method for making molal rather than molar solutions. For molar, always dissolve the material and then bring it up to the final desired volume