Perhitungan Dapar [PDF]

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1. Perhitungan Dapar pH sediaan : 4,9 – 7 pH dapar sitrat : 3,0 – 6,2 pKa1 : 3,128 pKa2 : 4,761 pKa3 : 6,369  pKa 6,396 Ka Ka



 β



mendekati H sediaan



= - Log Ka = - Log Ka = antilog 6,369 = 0,417 x 10-7 = 0,4017 x 10-6



= 2,303 x C x



0,01



 pH = 6 {H+} {H+}



Ka \{H + \} 2 (Ka+ \{H + \} )



= 2,303 x C x -6



-6



0 , 4 017 x 10 x 1 x 10 ( 1,4017 x 10 -6 + 1 x 10-6 ) 2 0,01



= 2,303 x C x



0 , 4 017 x 10 -12 ( 1,4017 x 10 -6 ) 2 0 , 4 017 x 10 -12 -12 1, 964 x 10



0,01



= 2,303 x C x



0,01



= 2,303 x C x 0,204 [g] pKa x Log [a]



 pH =



[g] = 6,396 x Log [a]



6



[g] 6 – 6,396 = Log [a] -1,2 [g] [a]



 C = 0,021 0,021 [a]



[g] = Log [a] = antilog 0,396



[a] = = =



+ [g] [a] + 0,401 [a] 0,401 [a] 0,014



- Log {H+} = - Log {H+} = antilog 6 = 1 x 10-6



 [g] = [g] [g]



0,401 [a] = 0,401 x 0,014 = 0,0056



 Massa = BM x Casam Asam = 210,14 x 0,021 = 210,14 x 0,0012 = 0,25 gram



x x



Volumesediaan 0,0618



 Massa = Garam = = =



BM x Cgaram 294,16 x 0,021 210,14 x 0,0021 0,352 gram



x x



Volumesediaan 0,0618



 %Asam



0,25 61,8



=



 %Garam =



0,352 61,8



x 100% = 0,4 % x 100% = 0,6 %