Given the balanced equation representing a reaction:
h+(aq) + oh-(aq) ==> h2o(l) + energy
in this reaction there is conservation of
(1) mass, only
(2) mass and charge, only
(3) charge and energy, only
(4) charge, energy, and mass

option (4) charge, energy, and mass.

Justification:

1) Charge, energy, and mass are always conserved in every chemical reaction.

Charge, energy and mass are not created nor destroyed, but can be transferred.

2) The charge can only be transferred by the motion of electrons, so the charge can move and end up on a different atom, but when you add up all the charge is conserved.

The charge balance is verified in the given equation since:

left side right side

(1+) + (1-) = 1 - 1 = 0 0

∴ The total charge of the reactants equals the total charge of the products.

3) As for energy, the right side shows the "apparition" of some energy. That means that the reaction is exothermic, i.e. it releases energy.

The energy released is the net result of the difference in the potencial chemical energy of the bonds of the products and the reactants.

The reactants have more chemical energy stored than the reactants, so potential energy was transformed into heat energy.

4) As for the mass, its conservation is verified when you check that there are the same number of particles of each spieces: two particles of hydrogen in the reactand side, such as in the products; and the particles of oxygen are one in the reactants and one in the products.

b.

the accuracy of the data.