Answer: 
is a reactant; it is present before the reaction occurs.
Explanation:
In a chemical reaction the chemical formulas written before the arrow are described as reactants as they react together to form products which are written after the arrow.
Thus and HCl are reactants here whereas 
, 
and 
are products.
Explanation:
Regulate body temperature in the extremes of space. maybe
Air moves from
high(pressure)the regions at the
poles(d0)
Do the atomic mass times the number of atoms you have. That'll give you your answer. Hope it helps!
