Jawabanmu

2014-03-30T18:09:31+07:00
Ka= 1,8 . 10^-4
500ml = 0,5 liter
pH = 8 + log 5
pOH = 6 - log 5
[OH-] = 5 . 10^-6

[OH-] = akar kw/ka . Mg
5.10^-6 = akar 10^-14 / 1,8.10^-4 . Mg
25.10^-12 = 10^-14 / 1,8.10^-4 . Mg
45.10^-16 = 10^-14.Mg
Mg = 45.10^-2

Mg = massa / Mr . Liter
45.10^-2 = massa / 68 . 0,5
45.10^-2 = massa / 34
massa = 1530.10^-2 gram
massa = 15,3 gram
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