Hitunglah pH jika 0,37 gram Ca (OH)2 dalam 50mL larutan

Diketahui :
m Ca(OH)2 = 0,37 gram
V larutan = 50 ml = 0,05 L

Ditanya : pH larutan ?

Jawab :

mol Ca(OH) :
= m / Mr
= 0,37 gram / 74 gram/mol
= 0,005 mol

Molaritas Ca(OH)2 :
= n / V
= 0,005 mol / 0,05 L
= 0,1 mol/L
= 10-¹ M

[OH-] :
= b . M
= 2 . 10-¹ M

pOH :
= – log [OH-]
= – log 2.10-¹
= – ( log 2 + log 10-¹}
= – log 2 – log 10-¹
= 1 – log 2

pH :
= 14 – pOH
= 14 – ( 1 – log 2)
= 14 – 1 + log 2
= 13 + log 2