Analitik kimyodan masalalar

Yechish:

Bufer sig`imi deganimiz (buffer capacity) ß – eritmaning pH –ni bir-birlikga ózgartirish uchun 1 litr bufer eritmaga qo`shilishi kerak boladigan kislota yaki ishqorning ekvivalent soni. Bufer sig`imi quyidagi formuladan topiladi:

B = n/(Z • V • ∆pH)

HCl – bir asosli, z = 1:

n(HCl) = CV = 0,030 • 0,1 = 0,003 mol;

V(bufer) = 0,08 l

B=  0,003/(1 • 0.08 • 1) = 0,0375 mol/l.
6-masala Massa ulushi 5% bolgan teng hajmli NН₄ОН va NН₄Сl aralashmasidan iborat bufer aralashmaning pH-ni hisooblang. 

Yechish:
К_w=1·10^–5;
M(NH₄OH) = 35 g/mol;

M(NH₄Cl) = 53,5 g/mol

w%(NH₄OH) = w%(NH₄Cl) = 0,5% yoki 0,005;

К_D(NH₄OH) = 1,76 · 10^–5 .

pH = ?

Ammoniy gidroksidi va ammoniy xloridining konsentrasiyasini tphamiz

Teng hajmdagi kislota va uning tuzi aralashtirilganidan so`ng konsentrasiya ikki marta kamayadi:

С_M(NH₄OH) = [w%(NH₄OH) · 1000]/M(NH₄OH) = (0,005 · 1000)/35 = 0,143 mol/dm³;
С_М(NH₄Cl) = [w%(NH₄Cl) · 1000]/M(NH₄Cl) = (0,005 · 1000)5/3,5 = 0,093 mol/dm³.