how do you know if a solid can be a hydrat given the mass before and after heating?
if a solid before heating has a molar mass of 208 g/mol and a formula of XY, what is the formula of the hydrate?
some cracker tins include a glass vial of drying material in the lid. this is often a mixture of magnesium sulfate and cobalt chloride indicator. as the magnesium sulfate abdorbs moisture(MgSO4 X 1H2O - MgSO4 X 7H2O), the indicator changes color from blue to pink (CoCL2 X 4H2O - CoCl2 X 6H2O). when this drying mixture becomes totally pink, it can be restored by heating in the oven. what 2 changes are caused by the heating?
1. If it weighs less after heating (to something like 105 degrees C---not higher than that) than before heating, then a hydrate is a very strong possibility.
2. For the formula of the hydrate you need more information. Such as the mass after heating or some way to get at that information.
3. The drying agent and the indicator (the cobalt salt) are losing water.
To determine if a solid can be a hydrate given the mass before and after heating, you would need to compare the mass of the solid before and after heating. If there is a significant decrease in mass after heating, it suggests that a hydrate was present, as the water molecules in the hydrate are driven off during heating.
In the given scenario, if the solid before heating has a molar mass of 208 g/mol and a formula of XY, we are looking for the formula of the hydrate. To determine this, we need to calculate the molar mass of the compound XY with the assumption that there are no water molecules in the formula. If we find any discrepancy between the calculated molar mass and the given molar mass, it indicates the presence of water molecules, making it a hydrate.
Regarding the cracker tin example, heating the drying mixture in the oven causes two changes:
1. Loss of water molecules: Heating the magnesium sulfate (MgSO4 x 1H2O) and cobalt chloride (CoCl2 x 6H2O) hydrates causes the water molecules attached to the compounds to evaporate. This results in a loss of water from both compounds, changing the ratio of water molecules to anhydrous (without water) compounds.
2. Color change: The cobalt chloride indicator in the drying mixture changes color from blue to pink when it loses water molecules. The initial compound, CoCl2 x 4H2O, is cobalt chloride hexahydrate (CoCl2 x 6H2O) and, upon heating, loses water, causing the pink color to appear.
By heating, both compounds become anhydrous and can be reused in the cracker tin for absorbing moisture.
To determine if a solid can be a hydrate given the mass before and after heating, you can follow these steps:
1. Measure the mass of the solid before heating.
2. Heat the solid to remove the water of hydration.
3. Measure the mass of the solid after heating.
4. Compare the mass before and after heating.
If the mass after heating is significantly lower than the initial mass, it indicates that the solid was a hydrate. The difference in mass represents the mass of the water that was lost during heating.
Now, let's move on to determining the formula of a hydrate given the molar mass of the solid before heating.
1. Calculate the molar mass of the compound by adding up the atomic masses of its elements. In this case, the molar mass is 208 g/mol.
2. Identify the elements present in the compound. Here, we have X and Y.
3. Determine the molar ratio between X and Y in the compound. This can be done by considering the molar mass of each element and comparing it to the overall molar mass of the compound.
4. Write the formula of the compound using the molar ratio. For example, if X has a molar mass of 40 g/mol and Y has a molar mass of 168 g/mol, the formula would be XY2.
Moving on to the cracker tin example, when the drying mixture of magnesium sulfate (MgSO4 X 1H2O) and cobalt chloride indicator (CoCL2 X 4H2O) becomes totally pink and requires restoration, heating is performed. The heating causes two changes:
1. The water molecules that were present in the hydrates are released as steam due to the heat, thus removing the moisture from the mixture.
2. The hydrate compounds undergo a physical change due to the loss of water molecules and may transform into anhydrous forms. In this case, MgSO4 X 1H2O transforms into MgSO4 X 7H2O, and CoCL2 X 4H2O transforms into CoCl2 X 6H2O.
These changes allow the drying mixture to be restored and continue its moisture-absorbing function.