Question

During the cooling of a fired crucible, water vapor condensed on the crucible wall before the crucible's mass was measured. The condensation did not reoccur following thermal decomposition of the hydrated salt in Part B. Will the reported percent water in the hydrated salt be reported too high, too low, or just right?

a. too high- the calculated mass of the crucible is so high the calculated mass lost is also high, producing a high % water.

b. just right- the condensed water will not affect the calculated % water

Answer 1

Too high - mass of hydrated salt would be lower than expected and the mass measurement of

the crucible and lid would be too high

Hydrated salt - higher, Anhydrous salt - lower, Water lost - higher

Answer 2

1. the % water is determined by the loss in mass after heating....
the water vapor condensed on the crucible wall before heating was lost in addition to the water of hydration.
excess mass was lost
which is interpreted as a higher % water in the hydrate than it actually would have had

======================================...

since the fired cruicible is handled with oily fingers AFTER its mass measurement.
&
since subsequently in part b, the oil from the fingers is burned off

it was never weighed before or after heating

it has no effect

Answer 3

the percent water in the hydrated salt be reported as being too low.
note:
the mass of water = sum of (mass of crucible without heating + mass of hydrated salt) - mass of crucible after heating
If water condensed on the crucible wall, the second term "mass of crucible after heating" will be higher, thus, the mass of water will be lower. the percent water in the hydrated salt be reported as being too low.