Exam 1: Chp 2 Flashcards
(27 cards)
What does it mean that water has a fluid network of H-bonds?
The H-bonds within liquid water are constantly breaking and reforming
How does water behave in the process of ionic compounds?
Surrounds the ions, breaking them apart, and forming hydration shells
Ions can clump together and form clathrates
What is a clathrate?
When molecules of one substance (water) entirely surrounds molecules of another
How does water behave in the presence of non polar compounds?
Form clathrates surrounding the non polar molecules, cause non polar molecules to clump together due to hydrophobic effect
How does water behave in the presence of amphipathic molecules?
the amphipathic molecules form micelles
What are micelles?
A gathering of amphipathic molecules with their hydrophobic parts directed in the center and their hydrophilic pants directed outwards
What is the hydrophobic effect?
Nonpolar molecules are pushed together by H2O molecules that are attracted to each other by H-bonds
What is the equation for pH?
pH = -log[H+]
What is the expression for pKa?
pKa = -log(Ka = [H+][A-]/[HA])
How is pH and acidity affected when a reaction has a lower pKa than another?
The compound with a lower pKa is more acidic, lower pH → the proton is more likely to be removed by base
How is pH and acidity differ when pKa of one compound is higher than another?
The compound with a higher pKa is less acidic, has a higher pH → likely protonated
How does electronegativity affect pKa and acidity?
decreases pKa, increases acidity
How does resonance affect pKa and acidity?
More resonance stabilization of the conjugate base decreases pKa and increase acidity
How does the inductive effect impact pKa and acidity?
Electron withdrawing groups near the acidic proton lower pKa and increase acidity
How does hybridization impact pKa and acidity?
More s-character lowers the pKa value and increases acidity
What are electron withdrawing groups?
Molecules that are electronegative
How does atom size impact pKa and acidity?
A larger atom distribute charge more which lowers the pKa value and increase acidity
Is the weak acid or conjugate base the predominant form when pKa < pH?
The conjugate base will predominate (deprotonated form)
Is the weak acid or conjugate base the predominant form when pH = pKa?
They are of equal concentrations
Is the the weak acid or conjugate base the predominant form when pKa > pH?
The weak acid will predominate (protonated form)
What is a buffer?
A solution that resists pH change by neutralizing acids or bases, either consisting of a weak and conjugate base or weak base and conjugate acid
What is the pKa of a buffer that works well in physiological conditions?
pKa of 6.4-8.4
Why are buffers important for biochemical processes?
The molecules in cells and in the body are sensitive to pH changes and buffers help resist them
Wha is the pH of physiological conditions?
Around 7.4
