A buffer solution composed of both Na2CO3 and NaHCO3 contains Na+ cations, CO3- anions and HCO3- anions. Na2CO3, or sodium carbonate, is a sodium salt of carbonic acid. It is composed of two Na+ ions and a carbonate anion. NaHCO3, or sodium bicarbonate, is composed of an Na+ ion and a bicarbonate anion. Both Na2CO3 and NaHCO3 are soluble in polar solvents, such as water.
A buffer solution has the ability to resist a change in pH upon the addition of either acids or bases in small amounts, according to Chemguide. Proper pH balance is achieved through the acceptance and release of H+ ions in the solution. According to Nassau Community College, there are three requirements for a buffer: it must be a mixture of a weak acid and its salt or a weak base and its salt, it must contain relatively large concentrations of acid to react with an added base and must contain a similar concentration of base to react with an added acid and the acid and base components of the buffer must not consume each other in a neutralization reaction. In a buffer system containing Na2CO3 and NaHCO3, the HCO3- anion from sodium bicarbonate acts as a weak acid. Na2CO3 is a salt of the weak acid H2CO3, or carbonic acid.