Explanation:
The given data is as follows.
[tex]M_{1}[/tex] = ?, [tex]M_{2}[/tex] = 0.85 M
[tex]V_{1}[/tex] = 185 mL, [tex]V_{2}[/tex] = 35.7 mL
where, [tex]M_{1}[/tex] is concentration of acid
[tex]V_{1}[/tex] is the volume of acid
[tex]M_{2}[/tex] is the concentration of base
[tex]V_{2}[/tex] is the volume of base
According to the neutralization formula.
[tex]M_{1} \times V_{1}[/tex] = [tex]M_{2} \times V_{2}[/tex]
Now, substituting the given values into the above formula as follows.
[tex]M_{1} \times V_{1}[/tex] = [tex]M_{2} \times V_{2}[/tex]
[tex]M_{1} \times 185 mL[/tex] = [tex]0.85 M \times 35.7 mL[/tex]
[tex]M_{1}[/tex] = 0.164 M
Thus, we can conclude that concentration of acid is 0.164 M.