A buffer solution has equal volumes of 0.1 ~M ~NH ₄ OH and 0.01 ~M ~NH ₄ Cl . The pK _b of the base is 5. The pH is

Step-by-step solution

The buffer solution consists of a weak base NH ₄ OH and its salt NH ₄ Cl . The concentration of the base [ B ] is 0.1 M and the concentration of the salt [ BH ^+] is 0.01 M after mixing equal volumes, as the dilution factor is the same for both. Using the Henderson-Hasselbalch equation for a basic buffer: pOH = pK _b + ( [ salt ] [ base ] ) Given pK _b = 5 , [ salt ] = 0.01 M , and [ base ] = 0.1 M : pOH = 5 + ( 0.01 0.1 ) pOH = 5 + (10⁻¹) = 5 - 1 = 4 The relationship between pH and pOH at 25^ C is pH + pOH = 14 .