Question

Sebanyak 3.16 gram (CH3COO)2Ca. (Mr=158) dilarutkan dalam air hingga volumenya 200ml. Jika Ka=2.10^-5. pH larutan tersebut adalah

Answer 1

Diket:
*n (CH3COO)2Ca = 3,16 gram / 158 = 0.02 mol
*M (CH3COO)2Ca = 0,02 mol /0,2 L = 0,1 M
 [CH3COO-] = 0,1 M x 2 = 0,2 M
*Ka = 2 x 10^-5

[OH-] = √Kw x [CH3COO-] / Ka
         = √10^-14 x 2 x 10^-1 / 2 x 10^-15
         = 10^-5

pOH = 5
pH = 14 - pOH
pH = 9