What volume of concentrated #HCl# contains a mass of #125*g# #HCl#?

The conc. acid you use in a lab is #34%# #w/w#. As a I recall, this has a density of approx. #1.17*g*mL^-1#.

We require #125*g*HCl# #=# #(125*g)/(36.46*g*mol^-1)# #=# #3.43*mol#.

For volume, we divide the molar quantity by the concentration:

#(3.43*cancel(mol))/(10.9*cancel(mol)*cancel(L^-1))xx1000*mL*cancel(L^-1)# #=# #315*mL#

But of course the questioner has not specified the concentration with which we work. We are guessing.

Working back, a volume of #283*mL# corresponds to #12.2*mol*L^-1#. This is very concentrated muriatic acid. The concentration of the acid should have been specified as a boundary condition.

It should be given here that #w/w%#of conc. Hydrochloric acid is #37.2%#
The calculation of volume will be as fillows.

As the density of #37.2%(w/w)# is #1.19g/(ml)# the volume of 100g #37.2%# conc hydrochloric acid will be #100/1.19(ml)# and this volume of conc. acid will contain #37.2g HCl#

Hence #125g# of conc.hydrochloric acid will be available from the volume
#100/1.19xx125/37.2 ml~~282.37ml" HCl"#

Concentrated hydrochloric acid has concentration of 12.19 mol/litre,

The molar mass of HCl is 36.458 g/mol.

125 g is therefore (125/36.458) = 3.4286 moles.

So the volume that would contain this number of moles is going to be (3.4286 / 12.19) = 0.28126 litres or 281.26 ml.