The Significance of pH Flashcards
What is the function of a buffer in living systems?
To maintain the pH of the body within normal pH ranges. This ensures that enzymes and other cellular processes function optimally.
What is the pH of blood?
pH 7.4
What is the pH of urine?
pH 6.0 (range 4.4 - 8.0)
What is the pH of gastric fluid?
2.2
What is the pH of saliva?
pH 6.2 - 7.2
What is the equation relating pH to the hydrogen ion concentration?
pH = -log10 [H+]
What do acids release when they dissociate?
H+ ions
What is an acid?
A substance which when in water tends to produce H+ ions
What is a base?
A substance which tends to combine with H+ ions
What is a conjugate acid-base pair comprised of?
A hydrogen ion donor (acid) and a hydrogen ions acceptor (base)
What is Ka?
The acid dislocation constant.
Ka = [H+] [B-] / [A]
The stronger the acid, the greater the Ka value, and the more the reaction is pushed to the right.
What is the Henderson-Hasselbalch equation?
pH = pKa + log10[B-]/[A]
The Henderson-Hasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant, Ka.
What are the effects on Ka, pKa and pH in the case of a strong acid?
Strong acid = larger Ka, smaller pKa and lower pH
What is an indicator?
Weak acids or bases which when in the ionised and unionised form shown a difference in colour.
The degree of dislocation and pH will be related by the equation:
pH = pKa + log10 [In-]/[HIn]
The colour change is determined by the pH.
What is a pH meter?
A more accurate method than indicators for measuring the pH of a given solution. Consists of a glass electrode (thin walled glass bulb containing a platinum electrode immersed in 1.0M HCl)
