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

How do I solve this?

The long way is to do each one. Assume 100 g sample and convert to grams CO2 which is the weight loss. For example, MgCO3, molar mass about 84.3

MgCO3 => MgO + CO2 and what you want is for CO2 to come out to be 36.1% (or 36.1 g from a 100 g sample).
mols MgCO3 = grams/molar mass = 100/84.3 = about 1.19
That will give you 1.19 mols CO2.
Convert that to grams CO2. 1.19 x molar mass CO2 = about 52.2 so MgCO3 is not the answer.

How do you get the 52.2? 1.19 x 36.1 = 43.0?

Oh Never mind.

To solve this problem, we need to understand that the weight loss during thermal decomposition of a carbonate is due to the release of carbon dioxide (CO2).

The key information provided is the 35.1% weight loss during decomposition. This means that 35.1% of the original weight is lost during the process.

To determine the unknown carbonate, we can calculate the remaining weight after the 35.1% loss for each option and see which option gives the closest result to the remaining weight.

For example, let's consider option A, Li2CO3:
- If the original weight of Li2CO3 is x grams, then after the 35.1% weight loss, the remaining weight is 0.649x grams (100% - 35.1% = 64.9%).
- Repeat this calculation for each option and check which one is closest to the remaining weight after the weight loss.

The remaining weights for each option would be:
A. Li2CO3: 0.649x grams
B. MgCO3: 0.649x grams
C. CaCO3: 0.649x grams
D. ZnCO3: 0.649x grams
E. BaCO3: 0.649x grams

By comparing these results, we can see that all options will have the same remaining weight after the 35.1% weight loss. Therefore, we cannot determine the unknown carbonate based on this information alone.

To further narrow down the options, additional information or experiments may be needed.