module 2: water Flashcards
what is an aqueous solution
water based environment
What is an example of a water based environment and what is produced
cytoplasm: DNA, protein and carbohydrates
what is the shape of water
bent: 104.5 degrees
is water polarized or non
polarized
define electronegativity
how do scientists show
atoms ability to attract electron to itself within a covalent bond
Dipole arrow points to more electron negative atom
what are 2 other polar molecules discussed
glucose- OH alcohol functional group
acetic acid-carboxyl functional group
what does the polar nature of water permit it to dissolve
other polar molecules
sugar, salts,
what happens when water is added to an oil and what do non-polar compounds have the ability to form
water pushes the oil away so two layers form
non-polar compounds( oil) has ability to form plasma membranes in cells
Define autoionization
a compounds ability to react with itself to form ions
what is the autoionization reaction for water and what results
H20+H20->H30+OH
water+water->Hydronium+Hydroxide
an acid and a base
neutral pH(7)
Does water have a lower or higher melting and boiling point
higher
allows for strong intermolecular forces
define heat of vaporization
amount of heat needed to change liquid to a gas for 1 gram of substance
does water taste good on its own?
no-
has salts added to give it good taste
what is the average intake of water/liquids in humans
900mL beverage- 1050 output urine
800mL food- 100mL feces
300mL metabolic- 850 ML sweat
2000 total intake-2000 total output
define a non-covalent force
force that occur between two molecules
ex: fat soluble vitamin dissolve in cellular membrane and oil and water separate in italian dressing
what needs to be present for an attraction between 2 molecules
positive and negative charges
in non-covalent forces: are the charges partial or full and why
partial- usually partial positive or partial negative- due to difference in polarity and electronegativity
what are 3 types of non-covalent forces
dipole-dipole
hydrogen bonds
london forces
What is unique about dipole-dipole interaction and when do they form
give example
common for polar molecules
go towards higher reaction polarity
forms when 2 molecules align dipoles to create attraction
acetone and glucose: which is reason acetone is liquid
at room temperature
dipole forces in acetone are strong therefore need to be overcome for vaporization to occur
Where does the dipole arrow point in HCL bond
dipole arrow points from H to CL
indicates CL partial negative charge: but the unequal sharing of electron and is not formal charge
results in polarized molecule
What would the HCL bond be similar to in comparison
a magnet with its positive and negative charge
H+ and CL-
what is the strongest class of intermolecular forces
dipole-dipole interactions
What are hydrogen bonds and how to they result
strongest class of dipole dipole interactions result from negative and positive partial charges
what two parts must be present for a hydrogen bond to occur
hydrogen donor- source of partial (+)
hydrogen acceptor- source of partial (-)
what must a H atom be bonded to act as hydrogen donor
covalently bonded to O, N, F
donor portion can only be one of the above atoms bonded to H
What is the hydrogen acceptor
does it have to be present in a hydrogen bond
pair of non-bonded electron on a seperate O, N, F
serves as source of partial (-)
yes
Can H donors and acceptors exist on different molecules and how do they interact
yes
any one H donor can interact with a different acceptor
What are 2 examples of hydrogen bonds
what shows the hydrogen bond
NH3+NH3 and water and methanol
4 parallel lines
how many hydrogen bonds does water form when it freezes?
about 4
3.7 to be most accurate
what is the critical reason water has unique properties
such as high boiling and melting point
hydrogen bonding
water molecule forms multiple H bonds: many H interacting
which bonds are the strongest non-covalent forces
hydrogen
which is why water has a much higher boiling point than other molecules
which interaction of forces is the weakest
london forces
how are london forces characterized
temporary collection of interactions of molecules that form partial (+) and (-) charges
what forms during a london force interaction
dipole forms due to random electron movement and is temporary- will come and then go- which is why weakest force
encourages strongest attraction at a moment before releasing
why do london forces exist
because electron move quickly into bunched confirmation and then fall apart
do repeatedly- molecules are not polar and ability to interact with other molecules
which bond is the strongest
covalent O-H: 400kcal
what is one key difference between covalent and non-covalent bonds
covalent bonds are permanent= stability
non-covalent are non permanent- but rather interactions with (+) and (-) partial charges- result in attractions- but reduced stability- allows for more biological processes including drugs bind to protein to help body fight disease
define hydrophilic and hydrophobic
water loving- hydrophilic
water fearing- hydrophobic
what happens when polar or charged molecules are added to water
interact to form hydrogen bonds or dipole-dipole interactions
what happens when non-covalent substance is added to water: i.e cooking oil
H atoms push oil away to form 2 layers- so water can maintain its strong non-covalent hydrogen bond
define hydrophobic effect
collection of nonpolar regions minimizes interactions with H2O- while polar region interact with water
what is the driving force behind the hydrophobic effect
spontaneous drive of water to bind itself through hydrogen bonds
what is the cage structure water orders itself around to maximize H bonds
clathrate( hydrophobic portion of nonpolar regions)
what is the physiological pH of a human cell
7.4
Define equilibrium
achieved when rates of forward/reverse reactions are equal
what is the equilibrium constant
way to describe rate to which the forward reaction occurs
aA+bB->cC+dD
what is the molar concentration of water
55.5M
what is K(w)
ion product of K equilibrium
1.0x10^-14
what is the equation to find pH
pH=-log(H+)
what is the pH of a lysosome
5
more acidic to help break down molecule
What is a strong acid and give examples
dissolves in water and ionization ability
HCL, sulfuric acid
what are strong bases and give examples
dissolves in water and complete ionization ability Sodium hydroxide(NaOH) and calcium hydroxide Ca(OH)2
what is more common to be present in biological solutions
weak acid/bases
what does weak mean in terms of ionization
partial ionization
dissolves in solution, then ionize to form H+ and the corresponding anion
what is an example of a weak acid
acetic acid- CH3(COOH)
produces acetate ion( CH3 COO) and proton (H+)
Looking at the ionization of acetic acid: which is the proton donor and acceptor?
proton donor: CH3COOH- generates H+ and donates
proton acceptor: CH3COO- in reverse reaction accepts H to recreate acetic acid
how do we generally characterize a weak acid
HA-> A(-) + H(+) and it can reverse
what is another name for the Ka constant
acid dissociation constant
can be used similarly to previous reactions with the regular equilibrium constant
what does a larger value of Ka indicate
stronger acid and more H+ ion
define buffer
aquauous system that resists change in pH with small amounts of H and OH added because of the weak acid or base has ability to react with or neutralize the added additions of acid or base
what is a specific buffer that aids in cell maintaining pH
dihydrogen phosphate
define buffering range
all react well within +1/- of pka range
example: acetic acid has pka of 4.82 and range is 3.82-5.82
what is buffering capacity
limit to amount of acids/bases added that can be neutralized
what is the bicarbonate buffer system
important in human body
set of 2 reactions that are reversible and connected
what are the two components of the bicarbonate buffer system
CO2 produced by cells react with water to from weak carbonic acid
carbonic acid then reacts to form bicarbonate ion and proton
effective at pH of 7.4
what are the physiological effects of the bicarbonate buffer system
in bloodstream: CO2 is transported from tissues to lung to be released
the kidneys/renal system balance the level of bicarbonate ions in the blood stream
the renal tubulars take up any excess HCO3-
therefore this system maintains proper pH in cells and extracellular fluids
what is the reaction for the bicarbonate buffer system
CO2+H20->H2CO3->H+HCO3-
what is enthalpy
heat content of a reaction
reflects amount and the kind of bond in system
dictated as (H)
What is entropy
(S)
measurement of random/disorder of components of chemical system
increased random =high entropy
decreased random with increased order= lower entropy
what is a general rule of thumb for the energy of aqueous solutions
reaction produces more product than reactant- increased entropy has occured
if reaction contain structures ordered than increase in enthalpy
what is Gib free energy equation
G=H-TS
what is the T in free energy equation
unit kelvin for temperature
what do scientists typically measure when thinking about gibs free energy
the change in H, S, or T therefore change or delta G
hard to measure precisly
when the change of G is negative
when the change of G is positive
the reaction is spontaneous
the reaction is not spontaneous and will not happen on its own-
what are the 3 measures when considering thermal chemistry
Enthalpy-H-heat
Entropy-S-order
gibs free energy: G=H-TS
what is the shape of water
Bent. The bond angle is 104.5 degrees
What is autoionization and how is it important to water
Autoionization is the ability of a compound to react with itself to form ions. One water molecule reacts with a second molecule to form two ions: H3O+ and OH-. These ions exist in small amounts in pure water and influence the chemistry of water.
name 3 non-covalent forces discussed in the module
london dispersion forces
dipole-dipole forces
hydrogen bonding forces
What type of non-covalent interaction is known as the strongest dipole-dipole force?
hydrogen bonding
How does the strength of London forces change with increasing molecular weight? Explain briefly.
As molecular weight increase, the strength of London forces also increase. This is due to the increased number of electrons in larger molecules. The larger number of electrons creates the potential of stronger temporary dipoles.
What is the concentration, in M, of water as a pure liquid?
55.5 M
Define Keq and Kw.
Keq is the equilibrium constant. Numerically, it is equal to the concentrations of equilibrium products (in M) multiplied together over the concentration of equilibrium reactants multiplied together.
Kw is called the ion product. It is, essentially, the Keq for water that is equal to 1.0 x 10-14; the formula is:
Identify the acid, conjugate base, and proton in the following reaction.
HCOOH->H+ + HCOO-
HCOOH is the weak acid
H+ is the proton
HCOO- is the weak conjugate base
A buffer system has a pKa of 8.5. What is its effective buffering range?
7.5-9.5
Weak acid A has a pKa of 3.2, while weak acid B has a pKa of 5.6. Is Weak acid A or B the stronger of the two?
Weak acid A is stronger because a smaller pKa indicates a stronger acid.
Ice melts at room temperature. What is the sign for LaTeX: \DeltaΔG in this reaction?
(-) negative. The reaction happens spontaneously.
What is the role of ATP in helping a non-spontaneous reaction occur?
It provides a source of energy to assist the reaction. ATP breakdown has a significant negative ΔG value.
