2KHCO3 ------> K 2CO3 + CO + H2 O
A student was asked to check the purity of a sample of potassium hydrogencarbonate.
The student weighed a clean, dry crucible, and transferred 1.00g of the potassium hydrogencarbonate to the crucible. A lid was placed on the crucible and the crucible was then heated for a few minutes. After cooling, the mass of the crucible and its contents was recorded.
Give one reason why the use of a lid improves the accuracy of the experiment.
State one reason why the use of a very small amount of potassium hydrogencarbonate could lead to a less accurate result.