A fictitious element X is composed of 10.0% of the isotope X-55, 20.0% of the isotope X-56, and 70.0% of X-57. Calculate the average atomic mass of element X

the answer is the first option

explanation:

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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.