Question

How many liters of 4 M solution can be made using 100 grams of lithium bromide?

Answer 1

Approx. `0.3*L`....

Explanation:

By definition, `"molarity"="moles of solute"/"volume of solution"`.

And here WE ASSUME, probably reasonably, that the volume of the resultant solution is LITTLE DIFFERENT to the volume of solvent used to make the solution. Do you appreciate the distinction I make here?

And so....

`underbrace(4*mol*L^-1)_"specified concentration"-=((100*g)/(86.85*g*mol^-1))/("Volume")`

And on rearrangement....

`"Volume"=((100*g)/(86.85*g*mol^-1))/(underbrace(4*mol*L^-1)_"specified concentration")=0.288*(L^-1)^-1=0.288*L`

Lithium halides are usually VERY soluble in aqueous solution, presumably because of the size mismatch between the ions, and these days such lithium salts are routinely prescribed to treat bipolar disorders.