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2. Diketahui :
Massa Ca(OH)2 = 0,74 gram
Mr Ca(OH)2 = 74
Volume = 2liter = 2000mL
Ditanya : pH?
Jawab :
Ca(OH)2 ➡️Ca2+ + 2OH-
Mb = gram/Mr x 1000/mL
Mb = 0,74/74 x 1000/2000
Mb = 0,01 x 0,5
Mb = 0,005
[OH-] = Mb x b
[OH-] = 0,005 x 2
[OH-] = 0,01
pOH = -log[OH-]
pOH = -log10^-2
pOH = 2
pH = 14-pOH
pH = 14-2
pH = 12

3. Diketahui :
Kb NH3 = 2x10^-5
NH3 = 0,2M
Ditanya : pH?
Jawab :
[OH-] = √Kb x Mb
[OH-] = √2x10^-5 . 2x10^-1
[OH-] = √4x10^-6
[OH-] = 2x10^-3
pOH = -log[OH-]
pOH = -log 2x10^-3
pOH = 3-log2
pH = 14-pOH
pH = 14 - (3-log2)
pH = 11+log2

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