The thermal decomposition of carbonates leads to the loss of CO2. The decomposition of an unknown carbonate leads to a 35.1% weight loss. The unknown was which of the following compounds.
A. Li2CO3
B. MgCO3
C. CaCO3
D. ZnCO3
E. BaCO3
To determine the unknown carbonate compound, we need to understand the concept of percent weight loss during thermal decomposition.
The percent weight loss is calculated by dividing the weight loss by the initial weight and then multiplying by 100. In this case, the weight loss is given as 35.1%.
Now, let's analyze each option to find the correct compound:
A. Li2CO3:
When Li2CO3 decomposes, it loses one CO2 molecule and forms two Li2O molecules. The molar mass of CO2 is 44 g/mol, and the molar mass of Li2CO3 is 73.9 g/mol. Since the decomposition only results in the loss of CO2, the weight loss from the decomposition of Li2CO3 would be approximately 60% (44 g / 73.9g * 100%). So, Li2CO3 is not the correct compound.
B. MgCO3:
When MgCO3 decomposes, it loses one CO2 molecule and forms one MgO molecule. The molar mass of CO2 is 44 g/mol, and the molar mass of MgCO3 is 84.3 g/mol. The weight loss from the decomposition of MgCO3 would be approximately 52.2% (44 g / 84.3g * 100%). So, MgCO3 is not the correct compound.
C. CaCO3:
When CaCO3 decomposes, it loses one CO2 molecule and forms one CaO molecule. The molar mass of CO2 is 44 g/mol, and the molar mass of CaCO3 is 100.1 g/mol. The weight loss from the decomposition of CaCO3 would be approximately 43.9% (44 g / 100.1g * 100%), which is close to the given weight loss of 35.1%. Therefore, CaCO3 is a possible correct compound.
D. ZnCO3:
When ZnCO3 decomposes, it loses one CO2 molecule and forms one ZnO molecule. The molar mass of CO2 is 44 g/mol, and the molar mass of ZnCO3 is 125.4 g/mol. The weight loss from the decomposition of ZnCO3 would be approximately 35.1% (44 g / 125.4g * 100%). Therefore, ZnCO3 is also a possible correct compound.
E. BaCO3:
When BaCO3 decomposes, it loses one CO2 molecule and forms one BaO molecule. The molar mass of CO2 is 44 g/mol, and the molar mass of BaCO3 is 197.3 g/mol. The weight loss from the decomposition of BaCO3 would be approximately 22.3% (44 g / 197.3g * 100%). Therefore, BaCO3 is not the correct compound.
Comparing the calculated weight losses, both CaCO3 (43.9%) and ZnCO3 (35.1%) are within close range to the given weight loss of 35.1%. However, the closest match is ZnCO3, which is the correct compound.
Therefore, the unknown carbonate compound is D. ZnCO3.