Calcium cyanamide (CaCN2) is a very versatile and powerful fertilizer. It can be produced easily fro — Physical Chemistry Chemistry Question
CaCN2 – An Old but still Important Fertilizer
Calcium cyanamide (CaCN2) is a very versatile and powerful fertilizer. It can be produced easily from cheap and common chemicals such as CaCO3. The thermal decomposition of CaCO3 leads to a white solid XA and a colourless gas XB which does not sustain combustion. A greyish solid XC and a gas XD form by the reduction of XA with carbon. XC and XD can be further oxidized. The reaction of XC with nitrogen finally leads to CaCN2.
How can calcium cyanamide be synthesized? Complete the reaction scheme below.
(1) CaCO3 T XA + XB
(2) XA + 3 C XC + XD
(3) XC + N2 CaCN2 + C
Model Answer
(1) CaCO3 T CaO + CO2
(2) CaO + 3 C CaC2 + CO
(3) CaC2 + N2 CaCN2 + C
This process that is technically important is called the Frank-Caro process.
What gas forms by the hydrolysis of CaCN2? Write down the equation of the reaction of CaCN2 with water.
Model Answer
CaCN2 + 3 H2O CaCO3 + 2 NH3
In solid state chemistry the CN2 2– ion shows constitutional isomerism. The free acids of both anions (at least in the gas phase) are known. Draw the structural formulas of both isomeric free acids. Indicate on which side the equilibrium is located.
Model Answer
The first compound is the acid of the carbodiimide ion, the second is that of cyanamide. The equilibrium favours the more symmetric structure.
(Inorg.Chem. 2002, 41, 4259 – 4265)