Select all of the following that have a standard enthalpy of formation equal to zero at 25°C and 1.0 atm?
Si (s)
H20 (1)
N2 (g)
Al (s)
CH4 (g)
H2O(g) Br2 (l)

Error 404 Error 404

Explanation:

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72