Question

У двох пробірках без написів є розчини солей калій карбонату та калій ортофосфату. Поясніть як би ви експериментально визначили кожну з цих солей. Вкажіть ознаки реакцій. Складіть рівняння відповідних якісних реакцій в молекулярному та йонному вигляді. Зробіть висновок

Answer 1

1) Н^+ : H2SO4 + K2CO3 = K2SO4 + H2O + CO2 (выделение газа)

CO3^2- + 2H^+ = CO2 + H2O

K3PO4 + H2SO4 X

2) Ag^+ : 3AgNO3 + K3PO4 = 3KNO3 + Ag3PO4 (жёлтый осадок)

3Ag^+ + PO4^3- = Ag3PO4

2AgNO3 + K2CO3 = Ag2CO3 (белый осадок) + 2KNO3

2Ag^+ + CO3^2- = Ag2CO3

Answer 2

Experimental Determination of Potassium Carbonate (K2CO3)

To experimentally determine the presence of potassium carbonate (K2CO3) in one of the test tubes, you can perform a simple acid-base reaction. Here's how you can do it:

1. Add a few drops of dilute hydrochloric acid (HCl) to the first test tube containing the unknown solution. 2. If potassium carbonate is present, it will react with the acid to produce carbon dioxide gas (CO2), water (H2O), and potassium chloride (KCl). 3. Observe the formation of effervescence (bubbles) and the release of carbon dioxide gas. This indicates the presence of carbonate ions (CO3^2-) in the solution. 4. To confirm the presence of potassium ions (K+), you can perform a flame test. Dip a clean platinum wire loop into the solution and hold it in a flame. The flame should turn violet or lilac, indicating the presence of potassium ions.

The qualitative reaction equation for the reaction between potassium carbonate and hydrochloric acid can be written as:

K2CO3 + 2HCl → CO2 + H2O + 2KCl

In the ionic form, the equation can be represented as:

K2CO3(aq) + 2HCl(aq) → CO2(g) + H2O(l) + 2KCl(aq)

Experimental Determination of Potassium Orthophosphate (K3PO4)

To experimentally determine the presence of potassium orthophosphate (K3PO4) in the other test tube, you can perform a precipitation reaction. Here's how you can do it:

1. Add a few drops of silver nitrate (AgNO3) solution to the second test tube containing the unknown solution. 2. If potassium orthophosphate is present, it will react with silver nitrate to form a yellow precipitate of silver phosphate (Ag3PO4). 3. Observe the formation of the yellow precipitate, which confirms the presence of phosphate ions (PO4^3-) in the solution. 4. To confirm the presence of potassium ions (K+), you can perform a flame test as mentioned earlier.

The qualitative reaction equation for the reaction between potassium orthophosphate and silver nitrate can be written as:

3K3PO4 + 4AgNO3 → Ag3PO4 + 3KNO3

In the ionic form, the equation can be represented as:

3K3PO4(aq) + 4AgNO3(aq) → Ag3PO4(s) + 3KNO3(aq)

Conclusion

By performing the suggested experimental tests, you can determine the presence of potassium carbonate (K2CO3) and potassium orthophosphate (K3PO4) in the respective test tubes. The formation of effervescence and the release of carbon dioxide gas, along with the violet or lilac flame color, indicate the presence of potassium carbonate. On the other hand, the formation of a yellow precipitate confirms the presence of potassium orthophosphate.