why might heating hydrates in a crucible to find the percentage of water in the hyrate not be appropriate for all hydates?

is it because some are flammable and water vapour might escape?

If you are trying to determine the percent water, you WANT the water vapor to escape. Some hydrates (either before or after driving out the water) may react with air (oxygen or nitrogen). And some hydrates don't lose all of their water of hydration at one temperature; that is, one mole of water may come off at 110 C and two more moles of water come off at 200 C. You can't control the temperature with a burner and crucible. Are there some hydrates that may react with the crucible?

aren't crucible made to not react with hydrates?

They will react with HF to form a gas. In fact, HF will eat a hole in the bottom of the xble.

thank you :)

Yes, you're correct. Heating hydrates in a crucible might not be appropriate for all hydrates for several reasons, including the possibility of flammability and the potential escape of water vapor. Here are a few reasons why this method might not be suitable for all hydrates:

1. Flammability: Some hydrates can be flammable or reactive when exposed to high temperatures. Heating these types of hydrates in a crucible could potentially lead to a hazardous situation, such as fire or explosions. Therefore, alternative methods must be used to determine the percentage of water in these hydrates.

2. Decomposition: Some hydrates can decompose or lose their water of hydration at temperatures lower than the desired heating temperature. If heating is carried out in a crucible, the hydrate may lose some or all of its water content before accurate measurements can be taken. This can lead to inaccurate results and an incorrect percentage of water being determined.

3. Water vapor escape: Hydrates often release water vapor when heated. In a crucible, the water vapor may not be fully contained, resulting in a loss of water and subsequently affecting the accuracy of the water percentage calculation. This can lead to an underestimation of the actual percentage of water in the hydrate.

To circumvent these limitations, alternative methods like gas-tight setups, thermogravimetric analysis, or techniques specifically designed for volatile or flammable hydrates can be employed. These approaches ensure accurate determination of the water content while maintaining safety precautions.