Areversible reaction a) always starts in equilibrium b) always starts off in the reverse direction c) always starts off in the forward direction d) always starts as a product and reacts to form reactions

A

Explanation:

A reversible reaction is a reaction in which under certain conditions, the product and reactant are in equilibrium with each other. Normal reactions starts with the reactant breaking bonds to have an unstable intermediate before producing the products. While in reversible reactions, the intermediate are usually a complex of both the product and reactant. Under a certain condition eg increase in pressure, the forward will be favoured or decrease in concentration of the reactant will favor the forward reaction while increasing it favor the backward reaction.

aA + bB ⇄ cC + dD

The above expression is an example of reversible reaction. (A and B) are both reactant while (C and D) are the products. However under normal conditions, they're at equilibrium with each other I.e the concentration of the reactant and products are equal.

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 !