Answers

2016-03-19T21:48:56+05:30
Bcoz it oxidise in the air and the deposition of magnesium oxide takes place on its outer surface.thats why it should be cleaned before burning.
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The Brainliest Answer!
2016-03-19T21:51:20+05:30
It should be cleaned because to remove a layer of oxygen ( mg oxide is formed on the mg ribbon when it is outside in the air )  so ,  to avoid disturbance 

hope helped u dear !! :)


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