Answer and Explanation:
Carbon dioxide (CO₂) dissolves in water and gives carbonic acid (H₂CO₃) which then dissociates first in HCO₃⁻ and then in CO₃⁻. So, its ionization increases the concentration of H⁺ and the solution becomes more acidic. If you measure the pH of a sample by using a colorimetric indicator and then you exhale your CO₂ in the sample, you will see that the indicator changes its color to the correspondent to a acid solution.
2 Na(s) + C(s) + 3/2 O₂(g) → Na₂CO₃(s)
Explanation:
The molar enthalpy of formation of a chemical is defined as the change in enthalpy during the formation of 1 mole of the substance from its constituent elements (Constituent elements are pure elements you have in the periodic table)
For Na₂CO₃ constituent elements are Na(s), C(s) and O₂(g) and the chemical equation that represents the molar enthalpy is:
2 Na(s) + C(s) + 3/2 O₂(g) → Na₂CO₃(s)