The pH of human blood is steady at a value of approximately...

The pH of human blood is steady at a value of approximately 7.4 owing to the following equilibrium reactions: $$\mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{H}^{+}(a q)$$ Acids formed during normal cellular respiration react with the $\mathrm{HCO}_{3}^{-}$ to form carbonic acid, which is in equilibrium with $\mathrm{CO}_{2}(a q)$ and $\mathrm{H}_{2} \mathrm{O}(l) .$ During vigorous exercise, a person's $\mathrm{H}_{2} \mathrm{CO}_{3}$ blood levels were $26.3 \mathrm{mM},$ whereas his $\mathrm{CO}_{2}$ levels were $1.63 \mathrm{mM} .$ On resting, the $\mathrm{H}_{2} \mathrm{CO}_{3}$ levels declined to 24.9 $\mathrm{mM}$. What was the $\mathrm{CO}_{2}$ blood level at rest?

The pH of human blood is steady at a value of approximately 7.4 owing to the following equilibrium reactions:
$$\mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{H}^{+}(a q)$$
Acids formed during normal cellular respiration react with the $\mathrm{HCO}_{3}^{-}$ to form carbonic acid, which is in equilibrium with $\mathrm{CO}_{2}(a q)$ and $\mathrm{H}_{2} \mathrm{O}(l) .$ During vigorous exercise, a person's $\mathrm{H}_{2} \mathrm{CO}_{3}$ blood levels were $26.3 \mathrm{mM},$ whereas his $\mathrm{CO}_{2}$ levels were $1.63 \mathrm{mM} .$ On resting, the $\mathrm{H}_{2} \mathrm{CO}_{3}$ levels declined to
24.9 $\mathrm{mM}$. What was the $\mathrm{CO}_{2}$ blood level at rest?

Key Concepts

Le Chatelier's Principle

Le Chatelier's Principle explains that when a system at equilibrium is subjected to a disturbance (such as changes in concentration, temperature, or pressure), the system will shift its equilibrium position to counteract the effect of that disturbance. This principle is fundamental in predicting how equilibria will adjust in response to various changes, including those occurring in biological systems.

Acid-Base Homeostasis

Acid-base homeostasis encompasses the mechanisms and processes that organisms use to maintain a consistent internal pH despite the production or ingestion of acidic or basic substances. This involves various equilibria and buffer systems that balance the concentrations of H+ ions to ensure optimal biological activity.

Buffer Systems

Buffer systems consist of a weak acid and its conjugate base (or vice versa) that work together to resist changes in pH when acids or bases are added to the system. This is crucial in biological systems, such as blood, where maintaining a stable pH is essential for proper cellular function.

Chemical Equilibrium

Chemical equilibrium refers to the state in a reversible reaction where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. This concept is key for understanding how systems respond to changes and maintain a steady state.

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