Chapter 4.9-4.11 Buffers, Buffer Capacity and Buffering in Blood ✓ Flashcards
What are buffers?
Buffers are solutions that have the ability to resist pH change when either acids or bases are added to them.
Generally, what will a buffer solution contain?
It will contain a weak acid-base conjugate pair meaning it can contain either an weak acid with a conjugate weak base or a weak base with a conjugate acid.
What allows buffer solutions to resist pH changes?
It allows to resist pH changes because the weak acid and its conjugate base (or weak base and its conjugate acid) coexist in equilibrium, neutralizing any added strong acid or base without reacting with each other.
What happens when a strong acid is added to a buffer solution?
It allows the buffer to resist pH changes because, according to Le Chatelier’s Principle, the conjugate base reacts with the added H⁺ ions, shifting the equilibrium left. This reduces the increase in H⁺ concentration, preventing a significant drop in pH.
What happens when a strong base is added to a buffer solution?
It allows the buffer to resist pH changes because, according to Le Chatelier’s Principle, the weak acid donates H⁺ ions to neutralize the added OH⁻, shifting the equilibrium right. This reduces the decrease in H⁺ concentration, preventing a significant rise in pH.
For this chemical equation, what are the conjugate pairs and explain why? NH₃ (aq) + HF (aq) ⇌ NH₄⁺ (aq) + F⁻ (aq)
HF is the weak acid, and F⁻ is its conjugate base because it donates it H+.
NH₃ is the weak base, and NH₄⁺ is its conjugate acid because it accepts HF H+
What does buffer capacity measure?
It measures the amount of acid or base the buffer can neutralize before the pH begins to change significantly.
When are buffers most effective?
Buffers are most effective when the concentrations of the weak acid and its conjugate weak base are similar, ensuring optimal buffering action.
How can a buffer solution have a high buffer capacity?
A buffer solution has a high buffer capacity when both the weak acid and its conjugate base are present in high concentrations. This allows the buffer to neutralize added OH⁻ (aq) or H₃O⁺ (aq) without significantly depleting either component.
Why is blood pH regulation important?
It is important because it maintains a healthy metabolic process and enzyme function.
What pH level must blood stay within?
Within 7.40-7.45. ph below 6.8 or above 7.8 can be fatal.
What is the main buffer system in blood?
The carbonic acid-hydrogencarbonate (bicarbonate) buffer system
What are the key components of the blood buffer system?
Carbonic acid (H₂CO₃) → Weak acid
Hydrogencarbonate (HCO₃⁻) → Weak conjugate base
How does the buffer system respond when blood pH drops (more acidic/ H+ increase)?
The equilibrium shifts left, producing more H₂CO₃ to remove excess H⁺.
How does the buffer system respond when blood pH rises (more basic, ↓ H⁺)?
The equilibrium shifts right, releasing H⁺ to lower pH.
What is the equilibrium reaction in the blood buffer system?
H2CO3(aq) ⇌ H+(aq) + HCO3−(aq)
Which organs help regulate blood pH?
Lungs and kidneys.
How do the lungs regulate blood pH?
Increased CO₂ shifts equilibrium right, lowering pH (more acidic).
Exhaling CO₂ shifts equilibrium left, raising pH (more basic).
How do the kidneys regulate blood pH?
They excrete H⁺ in urine, maintaining a normal pH range of 5.5 - 7.5.
What is another buffer system in blood besides the carbonic acid-bicarbonate system?
The dihydrogen phosphate (H₂PO₄⁻) / hydrogen phosphate (HPO₄²⁻) buffer system.
How does the buffer system prevent drastic pH changes?
It resists pH changes when acids or bases are added by shifting equilibrium accordingly.
What happens when 1 mL of 0.1 mol L⁻¹ HCl is added to 100 mL of blood vs. pure water?
-Blood: pH changes slightly due to buffering.
-Water: pH drops significantly because there is no buffer system.
What enzyme speeds up the buffering reaction in blood?
Carbonic anhydrase.
Textbook question
During vigorous exercise, the breathing rate increases, which increases the exhalation of CO2 from the blood. This effect plays a key role in restoring blood pH to normal levels. Using relevant equations and referring to Le Chatelier’s principle, explain how this process works.
1) CO2 + H2O ⇌ H2CO3 (Carbonic acid)
2) H2CO3 ⇌ H+ + HCO3- (Bicarbonate )
-Increased breathing rate leads to a faster rate of loss of CO2 from the blood from blood circulating in the lungs.
-This reduces blood CO2(aq) concentration
-As a consequence, the blood H2CO3(aq) conc. will also decrease followed by a decrease in H+ concentration and rising blood pH.
-These changes can be understood by Le Chaterlier’s principle.
-As the blood conc. of CO2 falls, equilibrium 1 shifts to the left minimising the imposed changes.
-This also results in decreased H2CO3 conc.
-Equilibrium 2 then shifts to the left producing more H2CO3 and minimising the effect of its reducing conc.
-As reaction 2 shifts to the left, it leads to a lower H+ conc. resulting in higher blood pH.
