Answer:

Explanation:
First, we find in the tables the ΔH of formation of each compound. As you can see in the (image 1)
Then we solve the ecuation for ΔH°reaction
ΔH°reaction=∑ΔH°f(products)−∑ΔH°f(Reactants)
ΔH°reaction= (-2* 393.5 - 2*285.8) - (52.4 + 0) kJ/mol
ΔH°reaction = -1.41 *10^3 kJ/mol
-<u><em>Oxygen</em></u>
According to Google these are the percentages of the <em>Earths Atmosphere</em>
<em>1</em> 78% - Nitrogen
<u>2</u> 21% - Oxygen
<em>3</em> 0.9% - Argon
<em>4 </em>0.3 - Carbon Dioxide with very small percentage of other elements.
Answer: 6 atoms in total
Explanation:
It has one sodium atom, one hydrogen atom, one carbon atom, and three oxygen atoms.
I think B
STEP-by STEP EXPLANATION
Answer:
it's an indicator that a chemical reaction occurred.