1.) Gas given off
2.) precipitate formed
3.) large amount of heat given off
4.) Color change
The given compound is
Each formula unit of has 2 mol Potassium (K) atoms, 2 mol Chromium (Cr) atoms and 7 mol Oxygen (O) atoms.
Atomic weight of potassium is 39.0983 amu
Atomic weight of Chromium is 51.9961 amu
Atomic weight of Oxygen is 15.9994 amu.
Therefore the formula weight of
= 294.1846 amu
In bleaching a stain, you see that the stain fades, and doesn't come back, which indicates that it has undergone a change.
Buring a match, you would see the ashes, and that it cannot be it's original substance again.
In rusting of an iron nail, the nail cannot be unrusted easily, which indicates that it has been through a chemical reaction.