In: Chemistry
if 0.050 mol of hcl is added to 1.0 l of buffer solution containing 0.125 M potassium acetate and 0.10 M acetic acid what is the change in PH of the solution
Potassium acetate reacts with HCl to produce acetic acid as per the reaction
CH3COOK + HCl -------->CH3COOH+ KCl
moles of potassium acetate (CH3COOK) in 1 L of 0.125M= Molarity* Volume(L)=0.125moles
moles of HCl = 0.050 moles, moles of acetic aicd in the buffer= 0.1*1=0.1 moles
HCl will be the limiting reactant,all the HCl gets consumed moles of acetic acid formed from the reaction =0.050
total of acetic acid =0.1+0.050=0.15, moles of potassium acetate remaining = 0.125-0.05= 0.075 moles
pKa of acetic acid= 4.76
pH= pKa+log [ potassium acetate]/[Acetic acid]
moles ratio of potassium acetate to acetic acid is equal to concentration ratio of potassium acetate to acetic acid
= 4.76+log(0.075/0.15)= 4.46