Passage III
As calcium oxalate hydrate (CaC2O4·H2O) is heated, it first dehydrates to yield calcium oxalate (CaC2O4). Next, the CaC2O4 decomposes into calcium carbonate (CaCO3) and carbon monoxide (CO). The CaCO3 then further decomposes into CaO and CO2 (see equations below).
CaC2O4·H2O(solid, s) 
CaC2O4(s) + H2O(gas, g)
CaC2O4(s)CaCO3(s) + CO(g)
CaCO3(s)CaO(s) + CO2(g)
In a thermogravimetric analysis (TGA), the mass of a sample is monitored as the sample's temperature is steadily increased. A nonreactive gas is streamed over the sample to carry away any gaseous products. The figure shows the results of a TGA of a 100 g sample of CaC2O4·H2O.
17. The CO2 that was part of the reactions that occurred during the TGA could best be described as a:
Your Answer is
Correct Answer is D
Explanation
Reactant reactant, product product. According to the last chemical reaction formula, CO2 is the product after the decomposition of CaCO3