In your experiment, you found that the hydrate MxXy*zH2O actually has six molecules of water associated with each formula unit, while the bottle indicated a formula with only four molecules of water. There are a few possible reasons for this discrepancy:
1. Measurement error: It is possible that there was an error in the measurement during your experiment, leading to a higher determination of water molecules. Double-check your experimental procedure and calculations to ensure accuracy.
2. Impurities: Sometimes, hydrate compounds can contain impurities that can affect the water content. If the hydrate you used had impurities, it could have resulted in a higher water content than indicated on the bottle.
3. Different hydrate form: It is also possible that there are different forms or types of the hydrate MxXy*zH2O, each with varying amounts of water molecules. The bottle you used might have contained a different form of the hydrate, one with only four molecules of water, while the one you tested had the form with six molecules of water.
To resolve this, you could repeat the experiment using a different sample of the hydrate, preferably from a reliable source, to verify the water content. Additionally, you can consult scientific literature or reputable sources to gather information about the hydrate's known forms and their respective water content. This will help ensure accuracy and provide a better understanding of the hydrate compound you are working with.