How would you make 1L of a buffer of pH=11 starting with 15g of base, C5H11N:. At you disposal are 1M HCl and 1M NaOH, pH meter, balance, distilled water and glassware. Try to be quantitative in expressing amounts of material that you will use. Given for C5H11NH+ pKa=11.25. Give the answer, step by step
I'll get you started. C5H11N is the base which I will call B. You have approx 0.18 mols in 15 g but you need a more accurate answer than that.
...........B + H^+ ==> BH^+
I.......0.18...0........0
add............x...........
C.........-x..-x.........x
E......0.18-x..0.........x
Substitute into the HH equation for
11 = 11.25 + log (0.18-x)/x
Solve for x and evaluate 0.18-x (remember to use the more accurate number you calculate)
x is millimols HCl to be added.
Convert that to ml 1 M HCl to be added to make a 1L solution of pH 11.
This is the calculated value; many then take a portion, place under a pH meter, and add HCl or NaOH dropwise and with stirring until the pH is exactly 11.00.