The question is incomplete, here is a complete question.
A solution is prepared at 25 °C that is initially 0.18 M in methylamine (CH₃NH₂), a weak base with [tex]K_b=4.4\times 10^{-4}[/tex], and 0.35 M in methylammonium bromide (CH₃NH₃Br). Calculate the pH of the solution. Round your answer to 2 decimal places.
Answer : The pH of the solution is, 10.36
Explanation :
First we have to calculate the value of [tex]pK_b[/tex].
[tex]pK_b=-\log K_b[/tex]
[tex]pK_b=-\log (4.4\times 10^{-4})[/tex]
[tex]pK_b=3.35[/tex]
Now we have to calculate the value of pOH.
Using Henderson Hesselbach equation :
[tex]pOH=pK_b+\log \frac{[Salt]}{[Base]}[/tex]
[tex]pOH=pK_b+\log \frac{[CH_3NH_3Br]}{[CH_3NH_2]}[/tex]
Now put all the given values in this equation, we get :
[tex]pOH=3.35+\log \frac{0.35}{0.18}[/tex]
[tex]pOH=3.64[/tex]
Now we have to calculate the pH.
[tex]pH+pOH=14\\\\pH=14-pOH\\\\pH=14-3.64=10.36[/tex]
Therefore, the pH of the solution is, 10.36
