Answer:

Explanation:
Assume the reaction is the combustion of propane.
Word equation: propane plus oxygen produces carbon dioxide and water
Chemical eqn: C₃H₈(g) + O₂(g) ⟶ CO₂(g) + H₂O(g)
Balanced eqn: C₃H₈(g) + 5O₂(g) ⟶ 3CO₂(g) + 4H₂O(g)
(a) Table of enthalpies of formation of reactants and products

(b)Total enthalpies of reactants and products

ΔᵣH° is negative, so the reaction is exothermic.
balance by putting 2 next to HF
-they are inside the nucleus of an atom
- they have a relative charge of +1
- they have a relative mass of 1
I’m just answering this so i can ask more questions and it has to be 20 words long so i hope you figure your problems out and merry christmas happy new year