Answer:
The pH is 2.74.
Explanation:
1st) We have to calculate the moles of H2CO3 contained in 0.20g, using the molar mass of the acid (62g/mol):
[tex]0.20g*\frac{1mole}{62g}=0.0032moles[/tex]Now we know that there are 0.0032 moles of H2CO3.
2nd) It is necessary to calculate the molarity of the solution:
[tex]\begin{gathered} 3,500mL-0.0032moles \\ 1,000mL-x=\frac{1,000mL*0.0032moles}{3,500mL} \\ x=9.14*10^{-4}moles \end{gathered}[/tex]The molarity of the solution is 9.14*10^-4 M.
3rd) We have to calculate the concentration of H+.
Since H2CO3 is a strong acid, it completely dissociates in aqueous solution. This is the dissociation euqation:
[tex]H_2CO_3\rightarrow2H^++CO_3^{-2}[/tex]When H2CO3 dissociates, 2 protons (H+) are produced, that's why the [H+] it is twice the [H2CO3].
So, the concentration of H+ is 1.83*10^-3 M.
4th) Now we can calculate the pH of the solution, by replacing the [H+] in the pH formula:
[tex]\begin{gathered} pH=-log\lbrack H^+\rbrack \\ pH=-log(1.83*10^{-3}) \\ pH=2.74 \end{gathered}[/tex]So, the pH is 2.74.
