Ihave this question for homework. but balancing chemical equations has never been my strong point can somebody explain it to me ?

3. when propane burns in air, it reacts with
oxygen (o2) to form carbon dioxide (co)
and water (h2o). which balanced chemical
equation describes this reaction?
a. c3hg + o2 + co2 + h2o
b. c3h8 + 402 co2 + 4h2o
c. c3h3 + 502 3c02 + h2o
d. c3hg + 502 → 3co2 + 4h2o

C₃H₈  +  5O₂  →  3CO₂  +  4H₂O

Option D.

Explanation:

This is a combustion reaction, where a compound reacts with oxygen to produce CO₂ and water.

You have to look at the reactants and the products.

C₃H₈  +  O₂  →  CO₂  +  H₂O

To balance you must have the same atoms of each elements in both sides.

Actually we have 3 C, 8 H and 2 O in reactant side and 1 C, 3 O and 2H in product side.

We can add 4 to water to have 8 H in product side to balance the H with reactants but we modified the amount of oxygens. Now, we have 4 O in water and 2 O from CO₂ (6 in total).

In reactant side, we have 3 C, therefore we add 3 to CO₂ and now, we have 3 C on both sides and 8 H in both sides, so, as in product side we have 10 O, 6 from CO₂ and 4 from water, we must add a 5 to balance in reactant side.  The balance equation will be:

C₃H₈  +  5O₂  →  3CO₂  +  4H₂O

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.