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thermal decomposition of basic copper(II)carbonate

if the value of mass of residue after decomposition is lower than expected then what does it mean?i know when its higher it means decomposition was incomplete bt dont get the lower part :confused:

its a question in cie P5 m/j08 any help would be much appreciated

(edited 10 years ago)

Was the salt dry?

nope it was a basic carbonate CuCO3.Cu(OH)2.H2O

Reply 3

Borek

Not exactly what I had on mind, but close.

Basic carbonate is a hydrate - and in most hydrates amount of water is not stable. Sure, there are exceptions, but as a rule of thumb if you see hydrate, be ready to assume its exact composition doesn't follow the formula. Number of water molecules can depend on the temperature, humidity and even on the sample history (what conditions it was stored in and for how long).

Reply 4

RRC

hmm so ur saying dat bcuz the mass of water in the carbonate will vary hence the initial mass v take before decomposition for a number of experiments will vary aswell so theres a chance that the anomaly is due to error in measuring the initial mass
i am understanding it correctly??