After removing a crucible (containing CaCO3 obtained as a precipitate) from an oven, what could you do (if you were being extremely careful and had enough time) to prove that the CaCO3 is dry?
Let the crucible and contents cool in a desiccator. Weigh accurately. Reheat the crucible and contents for an hour, cool, and reweigh. I like to see the same mass both times, at least to within 0.2 mg if this is being done on an analytical balance and it is standard quant and not semi-micro or micro quant.
To prove that the CaCO3 is dry after removing it from the oven, you can perform a simple experiment called a moisture test. Here's how you can do it carefully and ensure accurate results:
1. Allow the crucible and its contents to cool down to room temperature. This step is important as it prevents condensation and moisture absorption from the surrounding air.
2. Weigh the empty crucible using a balance and record its weight. This is your initial crucible weight.
3. Carefully transfer the CaCO3 precipitate from the crucible onto a clean, dry watch glass or porcelain plate using a spatula. Avoid any contact with moisture or water droplets.
4. Place the watch glass or porcelain plate with the CaCO3 in a dry location, away from any potential sources of moisture, such as an open container of water or a humid environment.
5. Leave the CaCO3 to dry for a sufficient amount of time. This duration can vary depending on the amount of moisture initially present and the environmental conditions. It is recommended to allow it to dry for at least 24 hours to ensure complete removal of water.
6. After the drying period, reweigh the crucible using the same balance and record its weight. This will be your final crucible weight.
7. Compare the initial crucible weight to the final crucible weight. If there is a significant difference in weight, it indicates that the CaCO3 still contains moisture. However, if there is no noticeable change in weight, it suggests that the CaCO3 is dry.
Remember, it is crucial to handle the crucible and its contents with care, ensuring no moisture comes into contact with the sample during the process.