1. What would happen if acid was added to this buffering system?

HA<===>H+ + A-

The acid shift to the right, producing H+ so the pH is maintained.
Is my answer correct?

2. Hydrocarbonate exists in equilibrium with carbon dioxide and water inside of a soda can. What will happen to the equilibrium if you shake the soda can?

If it shifts to right, pH goes up...Consider when adding the acid, it contains H+ ions,A-, and Ha

Adding more H+ will shift this to left. I assume your "if acid was added" is another acid, ie a strong acid.

1. Yes, your answer is correct. When an acid is added to a buffering system, it reacts with the base component of the buffer, causing the equilibrium to shift towards the right. In this case, the acid would react with A- (the base component) in the equation to produce more H+ ions. This reaction helps maintain the pH of the solution, preventing any significant change in acidity.

2. When you shake a soda can, you introduce mechanical agitation to the system. This causes an increase in the surface area and disrupts the equilibrium between hydrocarbonates, carbon dioxide, and water. As a result, the equilibrium shifts to restore balance by favoring the reaction that produces fewer gaseous molecules. In this case, shaking the soda can will lead to an increase in pressure, which ultimately forces more carbon dioxide to dissolve in the liquid. This explains why a shaken soda can appears to have more carbonation when opened compared to an undisturbed one.