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80 Cards in this Set
- Front
- Back
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What forms when water undergoes self-ionization?
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hydronium and hydroxide ions |
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What is an example of thermodynamic phenomena?
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any equilibrium process
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What determines the position of equilibrium?
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difference in free energy between reactants and products
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What is the constant concentration of water?
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55 M
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What is always the value of [H+][HO-] at equilibrium? |
1.0*10^-14
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How is pH calculated? |
pH = -log[H+]
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What is physiological pH?
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7.4
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What is a Brønsted-Lowry acid?
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proton donor
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What is a Brønsted-Lowry base?
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proton acceptor
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What is a Lewis acid? |
electron pair acceptor
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What is a Lewis base? |
electron pair donor
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What characterizes strong acids?
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complete dissociation in aqueous solution
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Give three examples of strong acids and their chemical formulas. |
nitric acid (HNO3) sulfuric acid (H2SO4) hydrochloric acid (HCl) |
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What characterizes weak acids? |
incomplete dissociation in aqueous solution
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Give three examples of weak acids. |
fatty acids nucleic acids amino acids |
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What describes equilibrium between a weak acid and its conjugate base?
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acid dissociation constant Ka OR pKa
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What describes the relationship between pKa and pH?
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Henderson-Hasselbalch equation
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What is the Henderson-Hasselbalch equation? |
pH = pKa + log[A-]/[HA]
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What can the Henderson-Hasselbalch equation determine? |
pH pKa [HA] |
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What is the pH of an aqueous 0.01 M solution of a weak acid HA that has a pKa of 5?
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3.5
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What is the most acidic proton of a polyprotic weak acid? |
the one with the smallest pKa value
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When does concentration of HA equal A-?
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after adding 0.5 equivalent
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What does one equivalent of base equal? |
number of moles (or molecules) of a strong base necessary to neutralize the same number of moles (or molecules) of a weak acid
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When does the pH of solution equal the pKa? |
after adding 0.5 equivalents of base to a weak acid
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What are buffers? |
mixtures of a weak acid and its conjugate base that resist change in pH when either strong acid or strong base is added
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What are buffers having a particular pH constructed from? |
weak acids having a pKa value plus or minus 1 pKa unit from desired pH
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When is there relatively little change in pH?
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broad range of pKa plus or minus 1 unit
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What is the pH of an aqueous 0.10 M solution of a weak acid HA that has a pKa of 6 and to which we add sufficient sodium hydroxide to produce a 0.05 M solution of the conjugate base?
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6
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Describe water's bonds. |
two polar, covalent bonds between oxygen and hydrogen
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What results in a dipole moment?
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unequal sharing of an electron pair due to differences in electronegativity
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What bonds of water are co-linear?
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OH---O hydrogen bond
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How strong is a hydrogen bond in relation to the strength of oxygen-hydrogen bonds?
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1/20th
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How long is a hydrogen bond in relation to the length of oxygen-hydrogen bonds? |
twice as long
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What kind of compounds dissolve readily? |
hydrophilic
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What happens to dissolved compounds? |
dissociated ions are surrounded by water molecules
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Give four examples of hydrophilic compounds.
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salts sugars polar molecules |
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What kind of compounds do not dissolve?
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hydrophobic
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Give two examples of hydrophobic compounds. |
hydrocarbons nonpolar molecules |
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What kind of compounds have both hydrophobic and hydrophilic features?
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amphipathic
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Give three examples of amphipathic compounds. |
detergents soaps lipids that make up biological membranes |
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What are five types of non-covalent interactions?
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electrostatic interactions hydrogen bonds hydrophobic interactions van der Waals contacts aromatic stacking |
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Describe the non-covalent interactions involved in the DNA double helix. |
hydrogen bonds between base pairs stabilized by van der Waals interactions |
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What is the hydrophobic effect?
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association of non-polar molecules with other non-polar molecules in aqueous solution
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What does the hydrophobic effect result from? |
combination of van der Waals interactions and increased entropy
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What is the hydrophobic effect important for? (3)
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protein folding ligand binding membrane formation |
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sphere of amphipathic molecules
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micelle
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ordered cage of ice-like water |
clathrate
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What is true about H+?
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Proton is associated with something, it's just easier to write it shorthand.
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What is the equilibrium constant of water?
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1.8*10^-16
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How do we know the equilibrium constant of water? |
measured experimentally
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How do electrons organize?
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as far away from each other as possible
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Why is water liquid? |
molecules rapidly moving
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Why can things diffuse through water? |
molecules rapidly moving
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Why are H-bonds in water so dynamic?
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It's easier for one proton to move than whole atoms.
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In what phase do humans do their chemistry in and why?
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liquid because of water
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What interactions occur between charged groups?
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electrostatic interactions
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What two things can electrostatic interactions be? |
attractive repulsive |
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What type of interactions are occurring when hydrocarbons pack up against each other away from water?
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hydrophobic interactions
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What is a challenge of hydrophobic interactions? |
electrons are being crammed together which is not energetically favorable, but oscillating temporary dipoles cause slight attraction
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Why do hydrophobic interactions occur despite their challenges?
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net negative free energy
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also called Lenard Jones interactions |
van der Waals contacts
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What are the transient dipoles that can cause small attractive forces? |
van der Waals contacts
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Describe aromatic stacking. (2)
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hydrophobic contacts permanent quadripoles because of the way electrons line up |
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What is true about the backbone of DNA? |
Polyphosphate backbone is easily ionized, avoids electrostatic repulsion because positive salts are present.
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What does the core of micelles consist of?
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hydrocarbons
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What happens immediately when something goes in water?
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hydrogen bonds break
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When is energy released in relation to microstates? |
when previously frozen water is released
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Why doesn't toxic heme kill humans?
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surrounded by protein
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What does heme do?
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carries iron atom that binds to oxygen which then transports O2 in the bloodstream
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apomyoglobin |
doesn't have heme
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What properties of water are important for biological interactions: polarity, density, or colligative?
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polarity and colligative
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properties that depend on the number of dissolved particles in solution, but not on the identities of the solutes |
colligative properties
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What happens to nonpolar molecules in water? |
They aggregate together.
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What drives the association of heme and myoglobin? |
The release of interfacial water.
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What is the H+ concentration in a urine sample that has a pH of 5?
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10^-5 M
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True or false: weak acids are completely dissociated in solution.
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false, incompletely dissociated
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How many equivalents of base need to be added to an acid solution for the pH to equal the pKa?
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0.5
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What is the ideal buffering range of the monoprotic acid MOPS, pKa = 7.2?
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pH 6.2 to 8.2
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What is the ratio of the acid to conjugate base at pH 7.0, if the pKa of the acid is 4.0?
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1 to 1000
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