9 A coefficient should always be added to balance an equation.
A to lower right of a chemical symbol.
B immediately before whatever element needs to be balanced.
C only at the beginning of a chemical formula.
D none of the above.

your answer would be a. 12.5 kg

i believe that it is a exoplanet

what is the question?

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.