Explain how calcium carbonate functions as a buffer. Include a chemical reaction in your explanation
7 years ago
Answered By Dennis Yuanjun C
A buffer works by resisting changes in pH. Remember that pH is only referring to the number of H+ in the solution so any other chemical that can resist changes in H+ will be a good buffer. Most buffer works by being in equilibrium between it's weak base and weak acid form. In this case CaCO3 (calcium carbonate) acts as a buffer in the bicarbonate form (HCO3). So CaCO3 will first disassociate into Ca2+ and CO3 2-, you will then need to add some acid into the solution to change CO3 into HCO3. (H+) + (CO3 2-) -> (HCO3-). In that form it can resist changes in pH by converting to either H2CO3 or CO3 2- in the following equations.
(H+) + (HCO3-) -> H2CO3 when acid is added to the solution, the extra H+ is absorbed into the bicarbonate and prevent most of the H+ from floating in the solution hence stabilizing the pH
(OH-) + (HCO3-) -> (CO3 2-) + H2O when base is added to the solution (OH-) it will absorb H+ in the solution. HCO3- will donate its hydrogen back into the solution to maintain the pH
7 years ago
Answered By Dennis Yuanjun C
A buffer works by resisting changes in pH. Remember that pH is only referring to the number of H+ in the solution so any other chemical that can resist changes in H+ will be a good buffer. Most buffer works by being in equilibrium between it's weak base and weak acid form. In this case CaCO3 (calcium carbonate) acts as a buffer in the bicarbonate form (HCO3). So CaCO3 will first disassociate into Ca2+ and CO3 2-, you will then need to add some acid into the solution to change CO3 into HCO3. (H+) + (CO3 2-) -> (HCO3-). In that form it can resist changes in pH by converting to either H2CO3 or CO3 2- in the following equations.
(H+) + (HCO3-) -> H2CO3 when acid is added to the solution, the extra H+ is absorbed into the bicarbonate and prevent most of the H+ from floating in the solution hence stabilizing the pH
(OH-) + (HCO3-) -> (CO3 2-) + H2O when base is added to the solution (OH-) it will absorb H+ in the solution. HCO3- will donate its hydrogen back into the solution to maintain the pH
Hope that answers your question