phosphate buffered saline (pbs) is a buffer solution commonly used in biological research. the buffer to maintain a constant ph. the osmolality and ion concentrations of the solution usually match those of the human body.

a. you need to prepare a stock solution at ph 7.00 with kh2po4 and na2hpo4 (pka =7.21). what would be the respective concentration of these substances if you wish to obtain the final phosphate concentration [hpo4 −2 ] + [h2po4 − ] = 0.3 m? no other information is given

b. what will be the ph of the solution after adding 0.18 l of 0.2 m naoh?

c. what is the ratio of hpo4 −2 of h2po4 – is part b, and what is the significance?

d. tris- hcl buffer is often used as a buffer for biochemical reactions in ph range from 7.1 to 9.1. it is made by dissolving in water tris (hydroxyl methyl) amino methane, a weak base, and then adding hcl. the conjugate acid-base pair for tris is (hoch2)3 c-nh3 + (here trish+ ) and (hoch2)3 c-nh2 (here tris base): its equilibrium is

(hoch2)3 c-nh3 + ↔ (hoch2)3 c-nh2 + h+ pka= 8.08 (at 25 o c)

assume you have to prepare 200 ml of the buffer. to do so you take 100 ml of 0.1 m tris base, add hcl and then adjust the volume with pure water. how many ml of 0.1 m hcl you have to add to it in order to have the final ph of ph = 8.0?