A scientist heated 6.50 g6.50\text{ g}6.50 g of hydrated cobalt(II) chloride in an open crucible to drive off its water of crystallisation.
The reaction is:
hydrated cobalt(II) chloride (solid)→anhydrous cobalt(II) chloride (solid)+water vapour (gas) \text{hydrated cobalt(II) chloride (solid)} \rightarrow \text{anhydrous cobalt(II) chloride (solid)} + \text{water vapour (gas)} hydrated cobalt(II) chloride (solid)→anhydrous cobalt(II) chloride (solid)+water vapour (gas)The scientist weighed the contents of the crucible after every 3 minutes of heating. The results are shown in the table below:
| Total heating time (minutes) | Mass of contents of crucible (grams) |
|---|---|
| 0 | 6.50 |
| 3 | 5.82 |
| 6 | 5.20 |
| 9 | 4.75 |
| 12 | 4.42 |
| 15 | 4.21 |
| 18 | 4.15 |
| 21 | 4.15 |
Find the minimum heating time needed for all of the water of crystallisation to be completely removed.
Calculate the total mass of water vapour released during the heating process.