C3H8 (g)+ 502 (g)  3CO2 (g) + 4 H2O (g) + 531 kcal

Exotérmica.

Explanation:

¡Hola!

En este caso, dado que la mayoría de reacciones de combustión son exotérmicas, al generar calor en los productos, es posible inferir que esta reacción, referida a la combustion de metano es exotérmica debido a lo anteriormente mencionado, ya que el término de energía de reacción, 531 kcal, está al lado de los productos, lo que quiere decir que es energía generada.

¡Saludos!

c most likely

hop this let me know if it is wrong

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !