Tolong di jawab ya cara no 20 kimia ya soalnya saya tidak tau caranya

NH3. + HCl. ==> NH4Cl
5 mmol. 5 mmol. 5mmol
Mg = 5 mmol / 100 ml = 5x10^-2 M

H+ = √ kw/kb x Mg
H+ = √ 10^-14/10^-5 x 5x10^-2
H+ = √ 5 x 10^-11
H+ = 2.2 x 10^5.5

pH = - log H+
pH = 5.5 - log 2.2