For metamorphism of rock to occur, temperature and pressure must
increase. Rocks created in this manner are called metamorphic
rocks.
Whenever any substance goes under chemical change so any of the reaction will happen either both or multiple compounds will combine to produce combination reaction either one compound will decompose itself into 2 or more compounds or elements and last one is replacement reaction the either reaction is not even going to combination nor decomposition, So when a reaction like that happens it must replacement reaction.
Now the question is what's the condition required for it, so basically a chemical reaction when takes place it depends upon several factor on the basis of which we conclude products. The factors are Temperature,catalyst,reagents, either what is the mechanism of reaction, stability of reactants and stability of products and alot more.
During reaction sometimes gas forms and sometimes not yea and well that also depends on the chemical reactivity and stability of product sometimes product found itself most stable releasing the gas evolving so it's been done itself and sometimes we add catalyst and adjust the reaction to extract that gas and get desirable product manually.
I wrote all i know if sorry if this is not what you're looking for :(
Answer:
The coefficient tells you how many molecules of that substance there is. The subscript tells you what the substance it. It tells you the the amount of each element there are in the molecule. Changing it would change the substance itself.
You could use distillation.
Hope this helps
