Please show all workings A buffer is prepared consisting of 0.75 mol of sodium d

Question

Please show all workings

A buffer is prepared consisting of 0.75 mol of sodium dihydrogen phosphate, NaH_2PO_4, and 0.60 mol of sodium hydrogenphosphate, Na_2HPO_4, dissolved in 600.0 mL of water. The K_a for the dihydrogenphosphate ion is 6.2 times 10^-8 at 25 degree C. Which of the following is another possible way to make the buffer described in the data set above? Select one: a. Add 0.6 mol of HCl to 1.35 mol of NaH_2PO_4 in 600.0 mL of water. b. Add 0.6 mol of NaOH to 1.35 mol of Na_2HPO_4 in 600.0 mL of water. c. Add 0.6 mol of HCl to 1.35 mol of Na_2HPO_4 in 600.0 mL of water. d. Add 0.6 mol of NaOH to 1.35 mol of NaH_2PO_4 in 600.0 mL of water.

Explanation / Answer

ANSWER

FIRST BUFFER MADE WITH ACID AND IT'S SALT, ACID GIVE ka VALUE AS WE SEE ABOVE DATA Ka VALUE GIVEN FOR NA[H2]PO4 SO WE CAN CHANGE ONLY IT..NOT NAHPO4, BECAUSE OPTION ONE HAVE BOTH ACID WHILE B &D HAVE NAOH WHICH IS NOT CORRECT REGARDING ACID BUFFER...ONLY ONE COMBINATION POSSIBLE ACID &IT SALT IS OPTION C..

BUFFER (A) pH= PKA +log [salt/acid]   

-log[6.2*10-8]+log[1.25/1]   

=7.30   

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