How many atoms are in 29.79 g of copper (Cu)?

2.80×10^23atoms

Explanation:

1mol of any element contains 6.02×10^23 atoms (Avogadro's constant)

1mole of copper is 64g

64g contain 6.02×10^23 atoms

29.78g will contain X atoms

29.79g × 6.02×10^23atoms= 64g×Xatom

X= 29.79g×6.02×10^23atoms/64g

X=2.80×10^23atoms

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.