How many moles are in 9.8 x 1024 atoms of calcium?

Explanation:

no of moles = no of atoms ÷ avogadro's number

= (9.8×10^24) ÷ (6.02×10^23)

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.