Amino Acids DLA. 2- Water, Bases And The Henderson-hassalbach Equation Flashcards
How does hydrogen bonds determine the “structure” water?
- As a liquid there are always 3-4 hydrogen bonds between water molecules, but water molecules are often tumbling
- when solid, there are always 4 hydrogen bonds between each water molecules(ice)
How do hydrogen bonds affect the thermal properties of water?
-Water has a large temperature range for a liquid state
CO2 in comparison is a gas at room temperature because it has no overall dipole
Why can water dissolve in polar substances?
Due to the permanent dipole
Water may…
Self-dissociate
Give equations for water self dissociating
H2O + H2O -> H30+ + OH-
What is the equation for pH?
pH= -log[H+]
Why may Mg(OH)2 be ingested?
Magnesium hydroxide (antacid, laxative) maybe ingested because it has very low solubility in water, (so some might argue about it being a strong base) but any that dissolves is dissociated
Why is Sulfuric acid considered weak ?
Only the first dissociation considered strong, HSO4- is a weak acid , compared to other weak acids it’s quite strong. But since it doesn’t completely dissociate in water, we call it weak
Titration: what is the equivalence point? Where is it found?
The equivalence point occurs when an amount of acid is mixed with an equal amount of base
The equivalence is found where 1/2 the region of sharp change in the curve
What is the correlation between Ka and acidity?
The higher the Ka the stronger the acid
What is the correlation between pka and acidity?
The lower the pKa the stronger the acid
What is the equation for pKa?
pKa = -logKa
Differentiate the Ka for a wHA and sHA
Ka for a wHA will not be as high as for a sHA
Differentiate the pKa of a wHA and a a sHA
pKa of a wHA will be larger than the pKa of a sHA
Assess the biological danger of a weak acid
Danger is not related to acid strength:
Ex. HF is a weak acid
- HF is toxic
- HF is toxic at any concentration
Vinegar is 5% acetic acid
Acetic acid is formed in metabolism
Or the same acid maybe toxic if concentrated
-Glacial(pure) acetic avid is toxic at high concentrations
What is the buffering region in titration?
The region where the pH changes slowly as H+ or OH- is added during a titration
How can the pKa be measured during titration?
Measured as the equidistant part of the curve which changes pH slowly.
When the pH= pKa of the weak acid, there is equal amounts of weak acid and its conjugate base (50% dissociated)
How do you find the effective buffering range for a weak acid?
This is when pH is +/-1 of the pKa of the weak acid
What are buffers?
Substances that resist a change in pH
How are buffers formed?
When a weak acid and a similar amount of its conjugate base are mixed, a buffer is formed
What are the major buffers in mammalian systems?
Carbon dioxide, phosphate and proteins
Why does phosphoric acid have 3 areas where it can act as a buffer?
It is a triprotic acid
What equilibrium constant of pure water?
Keq =[H2O]^2 = Kw= [ HC][OH-]= 10^-14
Give the pka formula
pka -logka
