This is the chemical reaction starting with carbon $C$ and proceeding through various compounds until we end up with potassium bicarbonate $KHCO3$. The steps involved are as follows:

C $carbon$ reacts with O2 $oxygen$ to form CO $carbonmonoxide$.CO reacts with more O2 to form CO2 $carbondioxide$.CO2 reacts with MgO $magnesiumoxide$ to form MgCO3 $magnesiumcarbonate$.MgCO3 decomposes to form CO2 and MgO again.CO2 reacts with K2O $potassiumoxide$ to form K2CO3 $potassiumcarbonate$.K2CO3 reacts with water to form KHCO3 $potassiumbicarbonate$.

Overall, the reaction involves a series of chemical transformations and is represented by the given steps.