Question

Gas evolved when a few crystals of KNO3 are heated in a hard glass test tube .

Answer 1

DURING THIS KIND OF REACTION OXYGEN GAS IS RELEASED[O2].


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Answer 2

Answer: Oxygen

Explanation: This is an example of thermal decomposition where one reactant is decomposed into two or more products by the use of heat energy.

$KNO_3(s)\rightarrow KNO_2(s)+O_2(g)$

Thus when a few crystals of $KNO_3$ are heated in a hard glass test tube, the bonds bwteen the reactants break due to absorption of ebnergy from heat and lead to formation of  potassium nitrite $(KNO_2)$ and oxygen gas $(O_2)$ is evolved.