pH of buffer solution can be calculated by Henderson-Hasselbalch equation. This equation needs three values to calculate pH. In this calculator, you can select different combinations of buffer solutions to determine pH value.
A buffer solution is defined as an aqueous solution which contains a weak acid and its conjugate base or a weak base with conjugate acid. pH of buffer solution slightly changes when a small amount of strong acid or strong base is added.
Please follow following steps to determine pH of buffer solution.
Here we are going to calculate pH of acetic acid and sodium acetate solution.
To show buffer characteristics, there should be enough acid and base concentration. First we should check the ratio of concentrations acetic acid and acetate ion (which gives basic property). pKa value of acetic acid is 4.75
Sodium acetate is a strong electrolyte and completely dissociates to sodium ion and acetate ion as below.
Because sodium acetate is dissociated completely, acetate ion concentration is 0.02 M.
Because ration is between 0.1 and 10, solution shows buffer properties. Therefore, we can continue to calculate pH of solution.
You were given 40 cm3 of 0.1 M ammonia solution and you have added 10 cm3 of 0.1 M HCl solution.
Ammonia and hydrochloric acid reacts with each other and form ammonium chloride. Ammonium ion shows acidic characteristics. Therefore, if both ammonia and ammonium chloride exist in a considerable concentration after the reaction, final solution can be a buffer solution.
Then, we should calculate how much ammonium chloride is formed and how much ammonia is still remaining in the final reaction.
Because, initial ammonia amount is higher than added amount of HCl, ammonia remains in the final solution with ammonium chloride (HCl is the limiting reagent). Let's calculate concentrations.
Ammonium chloride is a strong electrolyte in the water and dissociates as below.
Now, we can check the ratio of [base]/[acid] to get confirmed the solution is buffer or not.
Because ratio is located between 0.1 to 10, this solution is a buffer solution.