Term
Draw the structure of a water molecule, indicate the magnitude of the H–O–H bond
angle. |
|
Definition
|
|
Term
Explain the rationale for crystalline water’s (i.e. ice’s) having less density than liquid
water. |
|
Definition
The intermolecular contacts with crystalline water are mediated by hydrogen
bonds that are constrained to have precise geometries and distances. Except for
local order, liquid water does not have hydrogen bonding constraints, so water
molecules in liquid may interact through shorter distances than water molecules
in ice. In short, the hydrogen bonds in crystalline water keep the water molecules
separated. |
|
|
Term
| The equation relating force F to the dielectric constant D is |
|
Definition
|
|
Term
| Draw the chemical equations for the two-step ionization reaction of two water molecules. |
|
Definition
H2O → H+ + OH−
H+ + H2O → H3O+ |
|
|
Term
| Draw the chemical equation for the overall ionization of two water molecules. |
|
Definition
|
|
Term
Draw chemical equation for the predominant type of ionization of a single water
molecule. |
|
Definition
|
|
Term
Write the equation for Keq for the predominant type of ionization of a single water
molecule. |
|
Definition
|
|
Term
Write the equation defining the ion product of water, showing (1) its relation to
Keq, (2) its value (with units), (3) its relation to the concentrations of H+ and OH−. |
|
Definition
| Kw = 55.5Keq = 10−14M2 = [H+][OH−] |
|
|
Term
| Write the equation defining pH. |
|
Definition
|
|
Term
| Write the equation defining pOH. |
|
Definition
|
|
Term
| Write the equation defining pKw (include its value). |
|
Definition
|
|
Term
What is the pH of (1) household ammonia, (2) deionized water, (3) vinegar, (4) soft
drinks? |
|
Definition
(1) household ammonia : 11.4
(2) deionized water : 7
(3) vinegar : 2.9
(4) soft drinks : 2.8 |
|
|
Term
Vinegar is a good solution to clean bugs from a dirty windshield because its pH is
very low. Would a softdrink make a good alternative cleaner in the absence of any
available vinegar? |
|
Definition
|
|
Term
| What is the symbol for the acid dissociation constant? |
|
Definition
|
|
Term
The dissociation of acetic acid may be written:
Write the expression for the Ka for this reaction.
|
|
Definition
CH3COOH ↔CH3COO− + H+
[image] |
|
|
Term
Hydrochloric acid, HCl, dissociates completely in water.
What is the pH of an 0.01M aqueous solution of HCl? |
|
Definition
HCl → H+ + Cl−
pH = −log10 0.01 = 2 |
|
|
Term
| The dissociation of ammonium, NH+4 , may be written as: |
|
Definition
|
|
Term
| Write the Henderson-Hasselbalch equation. |
|
Definition
|
|
Term
Succinic acid has two acid dissociation constants, pK1 = 4.21 and pK2 = 5.63. Sketch
the titration curve for succinic acid against NaOH from 0 to 2 equivalents of NaOH. |
|
Definition
|
|
Term
| At what pH does a “buffer system” work best? |
|
Definition
| At the pKa of the weak acid. |
|
|
Term
| Draw a schematic for buffering action. |
|
Definition
|
|
Term
| Explain how buffers work. |
|
Definition
Buffers work by removing added or produced OH− or H+ from the system by
reaction with the weak acid (HA), to produce the conjugate base, or conjugate
base (A−), to produce the weak acid, respectively. As a result, changes in the
concentration of OH− or H+ are reduced significantly. |
|
|
Term
| Explain the rationale for the hydrophobic effect. |
|
Definition
Interactions between nonpolar molecules (or the nonpolar parts of molecules)reduce the hydrophobic surface area that is in contact with water. Because water organizes to create an ordered solvation shell around hydrophobic surfaces, the reduction of surface area reduces the amount of water required to be in the ordered solvation shells. This reduction in order corresponds to an increase in entropy. Because increases in entropy are generally thermodynamically favorable, interactions between nonpolar molecules (or the nonpolar parts of molecules) are
favorable in aqueous solution. |
|
|
Term
| Sketch a schematic of the cross-section of a micelle. |
|
Definition
|
|
Term
|
Definition
|
|
Term
| hydrophobic interaction/ hydrophobic effect |
|
Definition
the net attraction of nonpolar molecules (or different parts of
the same molecule) when in aqueous solution |
|
|
Term
|
Definition
| compounds that have both strongly polar and strongly apolar groups |
|
|
Term
|
Definition
clusters of amphiphilic molecules wherein the hydrophobic (apolar) parts of the
molecules |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
| a solution that resists changes in pH as acid or base is added |
|
|
Term
|
Definition
| a solution of a weak acid and it’s conjugate base |
|
|
