Question
How many millilitres of a 0.1 M solution of NaF and of 0.1 M solution of HF
must be mixed to obtain 1L of buffer at pH = 4? Ka = 6.7 × 10-4
Currently I am quite confident with using the henderson and Hasselbalch equation but this question has left me stumped...
Any help with the method of working this out would be greatly appreciated...
must be mixed to obtain 1L of buffer at pH = 4? Ka = 6.7 × 10-4
Currently I am quite confident with using the henderson and Hasselbalch equation but this question has left me stumped...
Any help with the method of working this out would be greatly appreciated...
Answers
DrBob222
How much buffer do you want? The problem doesn't say; if you can choose a volume, say choose 500 mL. Then let x = mL base and 500-x = mL acid, then in the HH equation it becomes
4.0 = pKa + log (0.1*x)/[(500-x)*0.1] and solve for x = volume of the NaF and 500-x is volume of HF. Should work ok; if 500 is not what you want substitute another number for that.
4.0 = pKa + log (0.1*x)/[(500-x)*0.1] and solve for x = volume of the NaF and 500-x is volume of HF. Should work ok; if 500 is not what you want substitute another number for that.