20 ~mL of 0.1 M acetic acid is mixed with 50 ~mL of potassium acetate. K_a of acetic acid =1.8 10⁻⁵ at 27^ C . Calculate concentration of potassium acetate if pH of the mixture is 4.8 .

Step-by-step solution

Let the concentration of potassium acetate is x . From Henderson's equation, aligned & pH = p K_a+ [ salt ] [ acid ] & 4.8=- (1.8 10⁻⁵ )+ x 50 20 0.1 M & 4.8=4.74+ 25 x aligned array rlrl or & 25 x=0.06 25 x & =1.148 & x=0.045 M array