Which of the following statements about balanced chemical equations is true?

they demonstrate that the number of atoms of each element is conserved during a chemical reaction.
they allow the theoretical masses of reactants and products in a chemical reaction to be calculated.
they provide the molar ratios of reactants and products in a chemical reaction.

The correct answer is They provide the molar ratio of reactant and products in a chemical reaction.

Explanation:

Balanced chemical equation helps us to calculate the number of moles of both reactant and product.For example

    2H2+O2=2H2O

From the above balanced equation it can be stated that 2 molecules of hydrogen(H2) reacts with 1 molecule of oxygen(O2) to form 2  molecules of water.

sry but any answer choices

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.