Answer:
In the second step, the chemist must measure 8.3 ml of concentrated acid
Explanation:
The concentration of the final solution can be obtained using the pH value:
pH = -log[H] = 0.60
[H] = 10^(-0.60) = 0.25 M
Then, the final concentration of HCl will be 0.25 M because HCl is a monoprotic acid, which means that HCl only has one hydrolyzable proton. Therefore: [HCl] = [H].
The number of moles of HCl in the final solution will be equal to the number of moles present in the volume taken from the stock solution:
n° of moles in the volume taken from stock solution = n° moles in the final solution.
The number of moles can be calculated as follows:
number of moles = concentration * volume
Then:
Ci * Vi = Cf * Vf
where
Ci = concentration of the stock solution
Vi = volume taken from the stock solution
Cf = concentration of the final solution
Vf = volume of the final solution
Replacing with the data, we can obtain Vi:
6.0 M * Vi = 0.25 M * 200.0 ml
<u>Vi = 8.3 ml</u>
