A person during a 24 hour period produced 1.40 litres of urine containing phosphate at a total concentration of 0.0440 M, at a pH of 6.00. This urine was made in the kidneys by acidifying the phosphate in the glomerular filtrate, which had a pH of 7.40. How much acid must be added to bring the pH of the glomerular filtrate from 7.40 down to 6.00? Assume a value of 6.80 for the pKa of the phosphate.

Question

A person during a 24 hour period produced 1.40 litres of urine containing phosphate at a total concentration of 0.0440 M, at a pH of 6.00. This urine was made in the kidneys by acidifying the phosphate in the glomerular filtrate, which had a pH of 7.40. How much acid must be added to bring the pH of the glomerular filtrate from 7.40 down to 6.00? Assume a value of 6.80 for the pKa of the phosphate.

I'm really not sure where to start this question... Henderson Hasselbach equation? I also have to determine the acid and the conjugate base in each phosphate pool.

Answer 1

I would think that the HH equation is the place to start. But I don't know enough about biochemistry to know the form of phosphate in each of the stages of the kidney. I suspect, however, that if you identify the pKa? of 6.80 (that is, is 6.80 pK1, pK2, or pK3, you will then know which acid/base pair to use and the rest is algebra.