Question

e) 9.0h + hbr3

1. mark and karen are carrying out a science project on the application of buffer solutions in the human body. they have discovered that a buffer of carbonic acid (h₂co₃) and hydrogen carbonate (h₂co₃) is present in blood plasma to maintain a ph of between 7.35 and 7.45. explain how this buffer, h₂co₃(aq) ⇌ hco₃⁻(aq) + h⁺(aq),

a. resists change in ph with addition of a small quantity of acid.
b. resists change in ph with addition of a small quantity of base.

Explanation:

Part a

Step 1: Identify buffer components

The buffer consists of weak acid $\ce{H2CO3}$ and its conjugate base $\ce{HCO3^-}$.

Step 2: Reaction with added acid

When a small amount of acid (e.g., $\ce{H+}$ from a strong acid) is added, the conjugate base $\ce{HCO3^-}$ reacts with the added $\ce{H+}$: $\ce{HCO3^-(aq) + H+(aq) -> H2CO3(aq)}$.

Step 3: Explain pH resistance

By consuming the added $\ce{H+}$, the concentration of $\ce{H+}$ in the solution does not increase significantly, thus resisting a large drop in pH. The equilibrium $\ce{H2CO3(aq) <=> HCO3^-(aq) + H+(aq)}$ shifts left to counteract the added $\ce{H+}$.

Step 1: Identify buffer components

Again, the buffer has $\ce{H2CO3}$ (weak acid) and $\ce{HCO3^-}$ (conjugate base).

Step 2: Reaction with added base

When a small amount of base (e.g., $\ce{OH-}$ from a strong base) is added, the weak acid $\ce{H2CO3}$ reacts with the added $\ce{OH-}$: $\ce{H2CO3(aq) + OH-(aq) -> HCO3^-(aq) + H2O(l)}$.

Step 3: Explain pH resistance

By consuming the added $\ce{OH-}$, the concentration of $\ce{OH-}$ does not increase significantly, so the pH does not rise much. The equilibrium $\ce{H2CO3(aq) <=> HCO3^-(aq) + H+(aq)}$ shifts right to replace the $\ce{H+}$ consumed by $\ce{OH-}$, maintaining pH.

Answer:

When acid is added, $\ce{HCO3^-}$ reacts with added $\ce{H+}$ to form $\ce{H2CO3}$, preventing a large pH drop. The buffer equilibrium shifts left to consume excess $\ce{H+}$.

Part b