The dying of eggs for Easter is a common family tradition throughout the United States. Reecall that a little bit of vinegar (a roughly 5% solution of acetic acid, CH3COOH, in water) is typically added to the mixture to help the dye adhere to the egg shell. The egg shell is mostly CaCO3, so the acetic acid reacts with carbonate to form H2O and CO2 (the formation of carbon dioxide bubbles form around the shell is visible), etching the shell and giving a greater surface area to absorb more dye.
The vinegar serves another role, however, that is less well known. The cuticle coating the shell contains polypeptides with —NH2 groups that stick out from the shell as shown in the illustration. The egg dyes, one of which is included in the illustration, generally carry a negative in charge.
A. What chemical reaction (besides the CO32- to CO2 reaction mentioned above) would explain why adding an acid to the dye adhere to the egg shell? (Note: the eggs dyes generally carry a negative in charge)
B. Utilize Ka values to support your answer.