Question

Tolong dijawab ya, nomor 4 dan 5
besok dikumpul jam 7 pagi.

Answer 1

4.) Penyangga basa
pH = 10 + log 2

pOH = 14 - (10 + log 2)
pOH = 4 + log 2

[OH⁻] = 2 x 10⁻⁴

mol NH₄Cl (garam) = 0,1 x 0,1 = 0,01 mol

[OH⁻] = Kb • mol basa/mol garam
2 x 10⁻⁴ = 10⁻⁵ • mol basa/0,01
20 = mol basa/0,01
mol basa = 20 x 0,01
mol basa = 0,2 mol
mol NH₃ = 0,2 mol

massa NH₃ = mol x Mr
massa NH₃= 0,2 x 17
massa NH₃ = 3,4 gram (Jawaban B)


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5.) Penyangga asam

pH = 5

[H⁺] = 10⁻⁵

[H⁺] = Ka • mol HCN/mol KCN
10⁻⁵ = 2 x 10⁻⁵ • mol HCN/mol KCN
10⁻⁵ / 2 x 10⁻⁵ = mol HCN/mol KCN
1/2 = mol HCN/mol KCN
mol HCN : mol KCN = 1 : 2


Apabila volume dianggap sama, maka perbandinagn mol = perbandinagn konsentrasi (M)

sehingga, M HCN : M KCN = 1 : 2 (Jawaban A)