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Lets say we have the following data:
Number of moles of NaCl = 3;
Density of NaCl solution = 1.25g/L;

Find molarity...
Molarity = No. of moles of solute/ volume of solution in L
we've been given the number of moles...but there isn't any way of finding the volume only from the density? ryt?

**EDIT: I got asked this question from my teacher and am pretty sure it's incomplete. All i want is a 'yes' if this question is solvable or a no, and maybe a hint as to how i'm supposed to find it? But im pretty sure we're missing some data here..

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    $\begingroup$ We have the policy which states that ‎you should explicitly show your thoughts, effort and attempts to understand underlying principles and solve the question. It'll make us certain that ‎we aren't doing your homework for you. ( As homework is considered literal homework, exams, self-study questions, puzzles, worked examples etc.) Please provide your full reasoning or thoughts on this, otherwise, the question may get closed.‎ See Homework $\endgroup$
    – Poutnik
    Aug 27, 2021 at 11:35
  • $\begingroup$ If 3 moles are suposed to be per litre, i.e. 3 M solution, than it is possible. If mot, there is still possible to derive molarity and molality for NaCl solution density table. $\endgroup$
    – Poutnik
    Aug 27, 2021 at 11:49
  • $\begingroup$ There is fixed relation between NaCl solution density and its molarity. 3 moles is excessive and furthermore absolute data, not saying to what volume or mass it is related. // But you should already know all of this. $\endgroup$
    – Poutnik
    Aug 27, 2021 at 11:55
  • $\begingroup$ @Poutnik hmm i think i found the solution..... density=m/v and molarity=moles/volume hence, molarity=density/molecular mass. Is that correct? $\endgroup$
    – Berty_Bert
    Aug 27, 2021 at 12:10
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    $\begingroup$ Hm, I see I have incorrectly read it as solution density 1.25 g/mL. The expression "Density of NaCl solution = 1.25g/L;" is nonsense, as they either mean g/mL, either mass concentration instead of density. $\endgroup$
    – Poutnik
    Aug 28, 2021 at 6:30

2 Answers 2

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All i want is a 'yes' if this question is solvable or a no, and maybe a hint as to how i'm supposed to find it?

No.

The points in the comments are excellent. You need to know something about the amount of water (assuming it is an aqueous solution) or the amount of the finished solution.

If you want to use a density table, you need the temperature. Oddly, the given density is much too low (if you go with the given units) or a little bit too high (if you change the units to kg/L like Sudhagar did in another answer). Here is a link to a density table for saturated aqueous solutions: https://pubs.usgs.gov/of/1984/0253/report.pdf

But im pretty sure we're missing some data here.

It is worse, the question would not make sense even if there is more data. Just ask your teacher for some more practice problems that are based on actual measurements rather than unrealistic values.

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The solution of the problem is nearly immediate. As the solution contains $1.25$ g salt per liter, its concentration is $\pu{\frac{1.25 g}{58.5g/mol} = 0.0205 mol L^{-1}}$. The total volume $V$ of your solution is unknown. But it contains $3$ mol $\ce{NaCl}$. As a consequence : $V$ = $\pu{\frac{3~ mol}{0.0205~ mol~ L^{-1}} = 146 L}$

Here we are ! No need of long calculations !

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