Page 59 - EBOOK ASAM BASA BERKONTEKS GREEN CHEMISTRY DAN SOCIO SCIENTIFIC ISSUES (SSI)

Contoh Soal 1

1.[H⁺] = 1,0 x 10⁻⁷ M
Maka,
pH = -log (1,0 x 10⁻⁷) log (10ᵃ) = a
pH = -(-7,00) = 7,00

2.[OH⁻] = 2,5 x 10⁻³ M

pOH = -log (2,5 x 10⁻³)
pOH = 3 – log 2,5 atau 3–0,40 = 2,60
Bila dijabarkan:
pOH = -log 2,5 x 10⁻³
pOH = -log 10⁻³ – log 2,5
pOH = 3 – log 2,5
pOH = 3 – 0,40 = 2,60

Maka,
pKw = pH + pOH
14 = pH + (3 – log 2,5)
pH = 14 – (3 – log 2,5) = 11 + log 2,5
atau
pH = 14 - 2,60 = 11,40

Contoh Soal 2

Jika suatu larutan NaOH memiliki pH 13, berapakah konsentrasi H⁺ dan OH⁻ dari
0,10 M larutan tersebut !

Solusi:
pH = 13
maka,
[H⁺] = antilog (-pH) = 10 -pH
[H⁺] = 10⁻¹³ M

Kw
[OH⁻]=
[H⁺]
1,0 x 10⁻¹⁴
[OH⁻]=
1,0 x 10⁻³

[OH⁻]= 1,0 x 10⁻¹ M

Jadi, larutan tersebut memiliki [H⁺] = 10⁻¹³ M dan [OH⁻]= 1,0 x 10⁻¹ M

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