[IK]

Dear All,

I need to calculate the concentration of a monohydrate salt in g/ml. I want to check if my calculation is correct.

I first measured 0.04g of the salt monohydrate.

The molecular weight (MW) of the salt monohydrate is 425.19528.
The molecular weight (MW) of the salt anhydrous is 407.18.

Therefore the mass of salt (anhydrous) is (407.18/425.19528)*0.04=0.038305223 g.

The mass of water in salt hydrate is then 0.04-0.038305223 = 0.001694777 g.

As density of water is 1g/ml then the vol of water in salt hydrate is 0.001694777 ml.

Then 40 ml water is added to dissolve the salt. There total vol of water is 40 + 0.001694777 =40.00169478 ml.

Therefore conc g/ml= (mass of salt anhydrous)/total vol of water =0.038305223/40.00169478=0.00095759 g/ml.

Is this calculation correct?

Best regards
IK

[sjb]

Seems reasonable - though check significant figures (and possibly density of water / the solution depending on how exact you need this)

[IK]

Ok. Thank you

[Arkcon]

As was said, you are seriously abusing significant figures.  You didn't measure to six digits, so you can't claim a calculation to six figures.

I'm not as sure as you seem to be, that volumes of a solid and solvent are additive.  See if that s justifiable.