By using the following formula we can calculate the volume;
C1V1 = C2V2
let V1 is the volume we have to find, then
C1 = 12.1m
C2 = 0.250m
V2 = 5 l
Now, C1V1 = C2V2
12.1 x V1 = 0.250 x 5
V1 = 1.25 / 12.1
V1 = 0.1033 l
thus, the 0.1033 liter of HCl is necessary.