30.14
Bufor fosforanowy
Układ buforowy fosforanowy jest kluczowym mechanizmem biologicznym utrzymującym stabilność pH w organizmie. Układ ten opiera się głównie na dwóch skła…
System buforów fosforanowych jest niezbędny w moczu i płynie wewnątrzkomórkowym.
Składa się z diwodorofosforanu sodu i wodorofosforanu sodu.
Ponieważ diwodorofosforan sodu jest słabym kwasem, nie dysocjuje zbytnio w roztworach kwaśnych i obojętnych.
Jednak po wprowadzeniu do roztworu mocnej zasady, takiej jak wodorotlenek sodu, diwodorofosforan sodu dysocjuje, oddając jony wodorowe. Jony te wiążą się z jonami wodorotlenkowymi, tworząc cząsteczki wody.
W tym samym czasie powstaje również wodorofosforan sodu.
Ponieważ proces ten przekształca wodorotlenek sodu w słabą zasadę wodorofosforanu sodu, pH roztworu wzrasta tylko nieznacznie.
Wodorofosforan sodu nie dysocjuje w warunkach zasadowych.
Ale po dodaniu do roztworu mocnego kwasu, takiego jak kwas solny, wodorofosforan sodu pobiera jony wodorowe, tworząc diwodorofosforan sodu.
Ponieważ proces ten przekształca HCl w słaby kwas, diwodorofosforan sodu, pH roztworu jest obniżone tylko nieznacznie.
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Q1: What are the two main components of the phosphate buffer system?
The phosphate buffer system consists of sodium dihydrogen phosphate (NaH2PO4), which acts as a weak acid, and sodium hydrogen phosphate (Na2HPO4), which serves as a weak base. These two components work together to neutralize both strong acids and strong bases, maintaining pH stability in urine and intracellular fluid.
Q2: How does the phosphate buffer respond when a strong base is added?
When a strong base like sodium hydroxide is introduced, sodium dihydrogen phosphate donates hydrogen ions that bind with hydroxide ions, forming water molecules. This converts the strong base into sodium hydrogen phosphate, a weak base, so the pH rises only modestly instead of dramatically.
Q3: What happens to the phosphate buffer when a strong acid is added?
When a strong acid like hydrochloric acid is added, sodium hydrogen phosphate accepts hydrogen ions and forms sodium dihydrogen phosphate. This converts the strong acid into a weak acid, causing only a slight pH reduction rather than a significant drop.
Q4: Why doesn't sodium dihydrogen phosphate dissociate in neutral or acidic solutions?
Sodium dihydrogen phosphate is a weak acid that does not fully dissociate under neutral or acidic conditions. It remains largely intact in these environments, but when exposed to strong bases, it readily donates hydrogen ions to neutralize the base and stabilize pH.
Q5: Where does the phosphate buffer system function in the body?
The phosphate buffer system is vital in urine and intracellular fluid, playing a critical role in renal physiology. It helps excrete hydrogen ions and stabilize urine pH, contributing to the body's overall acid-base balance through renal regulation of acid base balance.
Q6: What is the relationship between sodium hydrogen phosphate and strong acids?
Sodium hydrogen phosphate, the weak base component, neutralizes strong acids by accepting hydrogen ions released by the acid. This reaction binds excess hydrogen ions and converts the strong acid into sodium dihydrogen phosphate, a weak acid, preventing significant pH reduction.
Q7: How does the phosphate buffer system maintain pH stability?
The phosphate buffer system minimizes pH changes through its dual capacity to neutralize both strong acids and strong bases. By converting strong acids into weak acids and strong bases into weak bases, it effectively stabilizes the solution's pH even when significant amounts of acid or base are introduced.