Howard accidentally left the lid off while heating is hydrate. As the water boil

Question

Howard accidentally left the lid off while heating is hydrate. As the water boiled off , some of the solid anhydrate product spattered out of crucible. consider how this error would affect the following results: A How would the measured mass of anhydrate compare to the more accurate value Howard should have recorded?. B How would the mass of water lost compare to the more accurate value Howard should have calculated. C How would the percent water in hydrate compare to the more accurate value Howard should have calculated?

Explanation / Answer

Hydrate is a salt that contains water molecules of crystallisation. For example, CuSO4.5H2O. The formula contains the ratio of salt and water in a specific mole proportion. A dot is used between the formula of salt and formula of water. Once the salt is heated and the water molecules of crystallisation are lost, the salt is termed anhydrous.

A. Since, some of the anhydrous salt spattered out of the crucible, so, the mass recorded by Howard will be less than what it should be.

B. Since, Howard lifted the lid off, so, some vapours of water must have escaped the crucible. Hence, the mass of water lost as recorded by Howard would be less than the actual mass of water lost (because the vapours that have escaped could not be weighed)

C. Since the mass of water lost as recorded by Howard is less, hence, the percent water in hydrate would be less than the actual value. Exact value cannot be calculated as the exact amount lost is not mentioned. ( For example, if 10 moles of CuSO4. 5H2O are heated, they contains 50 moles of water molecules. Suppose, on heating 20 moles of water go away, then only 30 moles will be distributed among 10 moles of CuSO4. So, instead of 5 moles of water, each CuSO4 mole will have just 3 moles of water.)

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