Jika 200 mL NH4OH 0,8 M (Kb=1,0×10−5) direaksikan dengan 200 mL larutan HCl 0,8 M, pH campuran setelah bereaksi adalah adalah...

Pertanyaan

Jika 200 mL ${\mathrm{NH}}_4\mathrm{OH}$ 0,8 M ( $K_{\mathrm b}=1,0\times10^{-5}$ )direaksikan dengan 200 mL larutan HCl 0,8 M, pH campuran setelah bereaksi adalah adalah...

5 - log 2
5 - log 3
5 - log 4
5 - log 5
5 - log 6

Q. 'Ainillana

Master Teacher

Mahasiswa/Alumni Universitas Negeri Yogyakarta

Jawaban terverifikasi

Jawaban

jawaban yang benar adalah A.

Pembahasan

${\mathrm{NH}}_4\mathrm{OH}(aq)+\mathrm{HCl}(aq)\rightarrow{\mathrm{NH}}_4\mathrm{Cl}(aq)+{\mathrm H}_2\mathrm O(l)$

Garam ${\mathrm{NH}}_4\mathrm{Cl}$ merupakan garam hidrolisis asam yang terbentuk dari asam kuat HCl dan basa lemah ${\mathrm{NH}}_4\mathrm{OH}$ .

$\mathrm{mol}\;{\mathrm{NH}}_4\mathrm{OH}\;=\;0,8\;\mathrm M\;\mathrm x\;0,2\;\mathrm{mL}\\\mathrm{mol}\;{\mathrm{NH}}_4\mathrm{OH}\;=\;0,16\;\mathrm{mol}\\\\\mathrm{mol}\;\mathrm{HCl}\;=\;0,8\;\mathrm M\;\mathrm x\;0,2\;\mathrm{mL}\\\mathrm{mol}\;\mathrm{HCl}\;=\;0,16\;\mathrm{mol}$

Mencari konsentrasi ${\mathrm{NH}}_4\mathrm{Cl}$ terlebih dahulu

$open square brackets N H subscript 4 Cl close square brackets space equals space n over V open square brackets N H subscript 4 Cl close square brackets space equals space fraction numerator 0 comma 16 over denominator 0 comma 4 space L end fraction open square brackets N H subscript 4 Cl close square brackets space equals space 0 comma 4 space M$

$open square brackets H to the power of plus sign close square brackets space equals space square root of K subscript w over K subscript a x space open square brackets N H subscript 4 Cl close square brackets end root open square brackets H to the power of plus sign close square brackets space equals space square root of fraction numerator 10 to the power of negative sign 14 end exponent over denominator 1 space x space 10 to the power of negative sign 5 end exponent end fraction x space 0 comma 4 end root open square brackets H to the power of plus sign close square brackets space equals space 2 space x 10 to the power of negative sign 5 end exponent pH space equals space minus sign space log space open square brackets H to the power of plus sign close square brackets pH space equals space minus sign space log space 2 space x 10 to the power of negative sign 5 end exponent pH space equals space 5 space minus sign space log space 2$

Jadi, jawaban yang benar adalah A.

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