Question

Смесь карбоната калия и карбоната серебра обработали избытком раствора соляной кислоты. При этом выделилось 1,12 л (при н.у.) газа и образовалось 8,61 г осадка. Определите массовую долю (в %) карбоната калия в исходной смеси солей. В ответе запишите уравнения реакций, которые указаны в условии задачи, и приведите все необходимые вычисления.

Answer 1

1)      K2CO3 + 2HCl = 2KCl + CO2 ↑+ H2O

2)    Ag2CO3  +2HCl   =  2AgCl ↓ +CO2 ↑+ H2O 

 

AgCL –осадок и его масса известна по условию – 8,61 г Найдем его количество и узнаем сколько Аg2СО3 было в смеси и сколько выделилось углекислого газа

N=m/M= 8,61/143.5=0,06 моль AgCl   По уравнению соотношение соли и осадка 1:2 значит соли Ag2CO3 0,03 моль  масса m=0,03 * 276=8,28 г

Количество газа тоже 0,03 моль. Учитывая, что выделилось газа 1,12 л/22,4=0,05 моль, то 0,05-0,03=0,02 моль газа выделилось на первое уравнение.

Соотношение соли и газа в первом уравнении 1:1 значит K2CO3 было 0,02 моль Масса 0,02*138=2,76 г

Масса всей смеси 8,28+2,76=11,04г     W (K2CO3)=8,28/11,04=0,75=75%

Answer 2

Task Analysis

To solve this problem, we need to determine the mass fraction of potassium carbonate in the original mixture of potassium carbonate and silver carbonate. We are given the volume of gas evolved and the mass of the precipitate formed when the mixture is treated with an excess of hydrochloric acid. We also need to write the balanced chemical equations for the reactions involved and perform the necessary calculations.

Given Information

- Volume of gas evolved: 1.12 L (at standard temperature and pressure, n.t.p.) - Mass of precipitate formed: 8.61 g

Balanced Chemical Equations

1. Reaction between potassium carbonate and hydrochloric acid: ``` K2CO3 + 2HCl -> 2KCl + H2O + CO2 ```

Calculation Steps

1. Calculate the number of moles of carbon dioxide evolved using the ideal gas law equation: ``` PV = nRT ``` where: - P is the pressure (at n.t.p., it is 1 atm) - V is the volume of gas evolved (1.12 L) - n is the number of moles of gas (to be calculated) - R is the ideal gas constant (0.0821 L·atm/(mol·K)) - T is the temperature in Kelvin (273.15 K)

2. Calculate the number of moles of carbon dioxide using the equation: ``` n = PV / RT ```

3. Calculate the number of moles of potassium carbonate using the stoichiometry of the balanced chemical equation: - From the balanced equation, we know that 1 mole of potassium carbonate produces 1 mole of carbon dioxide. - Therefore, the number of moles of potassium carbonate is equal to the number of moles of carbon dioxide.

4. Calculate the mass of potassium carbonate using the molar mass of potassium carbonate (K2CO3): - The molar mass of K2CO3 is 138.21 g/mol.

5. Calculate the mass fraction of potassium carbonate in the original mixture: - The mass fraction is calculated by dividing the mass of potassium carbonate by the total mass of the mixture (including both potassium carbonate and silver carbonate) and multiplying by 100%.

Calculation

Let's perform the calculations step by step.

1. Calculate the number of moles of carbon dioxide: - P = 1 atm - V = 1.12 L - R = 0.0821 L·atm/(mol·K) - T = 273.15 K (n.t.p.)

   n = PV / RT
     = (1 atm * 1.12 L) / (0.0821 L·atm/(mol·K) * 273.15 K)
   

2. Calculate the number of moles of potassium carbonate: - From the balanced equation, we know that 1 mole of potassium carbonate produces 1 mole of carbon dioxide.

3. Calculate the mass of potassium carbonate: - The molar mass of K2CO3 is 138.21 g/mol.

4. Calculate the mass fraction of potassium carbonate: - The mass fraction is calculated by dividing the mass of potassium carbonate by the total mass of the mixture (including both potassium carbonate and silver carbonate) and multiplying by 100%.

Let's perform the calculations now.