Answer :
The original concentration of the acid solution is 6.175 [tex]\times[/tex] 10^-4 mol / L.
Explanation:
Concentration is the ratio of solute in a solution to either solvent or total solution. It is expressed in terms of mass per unit volume
HBr + NaOH -----> NaBr + H2O
There is a 1:1 equivalence with acid and base.
Moles of NaOH = 72.90 [tex]\times[/tex] 10^-3 [tex]\times[/tex] 0.25
= 0.0182 mol.
[ HBr ] = moles of base / volume of a solution
= 0.0182 / 29.47
= 6.175 [tex]\times[/tex] 10^-4 mol / L.