I would like to make an NaCl and water solution with a density of 1.2 g/ml. How would you calculate the grams of NaCl required to make a 1000 ml solution?

I have used density of mixture = (mass NaCl + mass H2O)/1000 ml and solved for the mass of NaCl. However, the resulting mass does not give a density of 1.2 g/ml in practice (and in fact does not dissolve) so is there another way of calculating this? (at room temperature (~21 °C))

  • $\begingroup$ The density also depends on the temperature.. $\endgroup$
    – ParaH2
    Mar 8, 2016 at 22:40

2 Answers 2


To answer in detail Jan, I didn't make stranged calculus, now I answered more than a year ago I can't tell you if my calculus are the same, but here is the logic.

For any solution (aqueous) we have, $$m_{solution}=\rho_{solution}\times V \tag1$$

We also have, $$\rho_{solution}=d\times \rho_{water} \tag2$$

where d is the relative density of the solution and then, merging both $(1)$ and $(2)$, $$m_{solution}=d \times \rho_{water}\times V \tag3$$

The mass of solute in the solution is a percentage of the masse of the whole solution then, because,

$$n_{solute}=\frac{m_{solute}}{M_{solute}} \tag4$$

We have,

$$n_{solute}=\frac{p\times d \times \rho_{water}\times V}{100\times M_{solute}}\tag5$$

Then find my previous result with $C\times V=n_{solute}$.

Now I think everyone is able to goes from molar to mass concentration then I can stop here. If not ask me.


The answer is: as much as water can dissolve.

The density of saturated sodium chloride in water at 21°C is $1.20~\pu{g cm^{-3}}$.

So you may take roughly $1000~\pu{ml}$ water of 21°C and put in sodium chloride such that not all of it can be dissolved (it will take some 400 grams). From the resulting solution‘s supernatant take $1000~\pu{ml}$.

  • $\begingroup$ table of densities at 60 F (15.5 C). brinemaker.com/TechnicalDocument/Sodium-Chloride-Table.pdf $\endgroup$
    – MaxW
    Oct 9, 2017 at 4:26
  • $\begingroup$ How do you do if in your laboratory water is at 25°C ? :-) $\endgroup$
    – ParaH2
    Oct 9, 2017 at 15:32
  • 1
    $\begingroup$ At 25°C and normal pressure there exists no such thing as sodium chloride solution with a density of 1.2000 g/ml (as requested). You had to live with a density of about 1.1978 g/ml which is 1.2 g/cm when rounded to two significant figures. ;-) $\endgroup$
    – aventurin
    Oct 9, 2017 at 18:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.