Water and Molecular Interactions

Question 1

Organisms are ___-___% water

Answer 1

70/90

Question 2

Water is held together by ____ bonds

Answer 2

Hydrogen

Question 3

____ biomolecules are highly soluble in water

Answer 3

Polar

Question 4

Why do polar molecules dissolve better in water than non polar?

Answer 4

Nonpolar biomolecules interfere with the water-water interactions, they decrease the entropy

Question 5

What are some characteristics of water? Why?

Answer 5

• Relatively high melting, boiling, and vapour point
• High surface tension
  Caused by attractions between individual water molecules

Question 6

In water molecules the hydrogen have partial ____ charges and the oxygen has a partial _____ charge

Answer 6

Positive/negative

Question 7

Why do water molecules have high attraction to each other?

Answer 7

Their partial positive and negative charges attract between molecules

Question 8

When water is heated, bonds break and reform _____. Cohesion is ______.

Answer 8

Rapidly/high

Question 9

Why doe side have a high melting point?

Answer 9

Water molecules are held in place by a crystalline structure

Question 10

What is ΔH?

Answer 10

Enthalpy change

Question 11

What is ΔG?

Answer 11

Change in free energy

Question 12

What is Δs?

Answer 12

Change in entropy

Question 13

Melting and evaporation occur ______ at room temperature, why?

Answer 13

spontaneously, tendency to bond is outweighed by the push to randomness

Question 14

During melting or evaporation ______ increases

Answer 14

Entropy

Question 15

H bonds for between _____ and _______, this excludes bonds formed between ______ and _______, which are weakly polar

Answer 15

hydrogen/electronegative atoms/hydrogen/carbon

Question 16

What other types of solutes does water readily dissolve (aside from polar solutes)? How?

Answer 16

• Charged solutes, done by stabilizing the ions which weakens the electrostatic interactions between them which limits their tendency to bond
• compounds with functional groups, done by replacing the solute-solute H bonds

Question 17

H bonds are strongest in a ______ line

Answer 17

Straight

Question 18

What are amphipathic biomolecules? Include examples

Answer 18

Molecules that are stabilized by their hydrophobic effect, they are important structural determinants, they have both hydrophobic and hydrophilic parts
-ex. proteins, pigments, some vitamins, sterols, membrane proteins

Question 19

Van der Waals interactions happens when two _____ molecule are brought close to each other, their _____ _____ influence each other, creating random ______ generation in both atoms which makes weak ______.

Answer 19

uncharged/electron clouds/dipole/attractions

Question 20

Each atom has a distinct Van der Waals _____

Answer 20

radius

Question 21

_______ and _______ bonds depend on solvent _____ an H ______

Answer 21

ionic/H/polarity/alignment

Question 22

Solutes can alter _____ _____ of solvents because they change the _____ of the solvent. These include ____ ____, ______ ______, ______ ______, _____ _____, and _____ _____.

Answer 22

Physical properties/concentration/melting point/boiling point/freezing point/osmotic pressure/vapour point

Question 23

In a hypertonic solution, water _____ the cell because solute concentration in the cell __ solute concentration outside the cell.
This causes animals cells to _____ and plant cells to _____.

Answer 23

leaves/<

shrivel/shrivel

Question 24

In hypotonic solution, water ____ the cell because solute concentration inside __ solute concentration outside.
This causes animal cells to ____ and plant cells to become ______ which is ____.

Answer 24

enters/>

lyse/turgid/ideal

Question 25

In isotonic solutions, water _____ and ____ the cell at an ____ rate, solute concentration outside cell __ solute concentration inside cell. This causes animal cells to be ____ and plant cells to be _____.

Answer 25

enters/exits/= | normal/flaccid

Question 26

Water ionizes to ___ and ___, this is described by the ___ constant. Pure water is ____ ionized.

Answer 26

H+/OH-/slightly

Question 27

Weak ____ that dissolve in water contribute ___, called ____. Weak ____ consume ___, called ____.

Answer 27

acids/H+/ionizing/bases/H+/protonating

Question 28

Water ionization is _____.

Answer 28

reversible

Question 29

pH: total ___ ______ from all sources in a solution

Answer 29

H+ concentration

Question 30

Even though H2OH+ +OH- is commonly shown as the equation for water ionization, ____ does not naturally exist in H2O and form ____ immediately instead

Answer 30

H+/H3O+ (hydronium ions)

Question 31

How can ionization be measured?

Answer 31

Electrical conductivity

Question 32

What is the equilibrium constant?

Answer 32

Keq: the position of equilibrium for every equation | Keq=[product of products Keq]/[product of reactants Keq]

Question 33

Ions ____ ____ in their individual directions based on _____, since ___ is especially fast is explains why acid/base reactions are so fast

Answer 33

proton hop/charge/H+

Question 34

Ionic product of water (Kw) = ?

Answer 34

Kw = Keq*[H2O] = [H+][OH-] = 1*10^-14 M^2

Question 35

pH = ?

Answer 35

``` pH = -log[H+] pH = 14-pOH ```

Question 36

pOH = ?

Answer 36

``` pOH = -log[OH-] pOH = 14-pH ```

Question 37

Strong acids and bases ionize ____.

Answer 37

Completely

Question 38

Acids are proton ____ and bases are protons _____.

Answer 38

Donors/acceptors

Question 39

Conjugate acid-base pairs:

Answer 39

Acids that pair with a base to donate and accept electrons, these are reversible reactions

Question 40

The tendency of an acid to lose a proton and form its conjugate base is defined by:

Answer 40

Keq = [H+][A-]/[HA] = Ka

Question 41

Ka represents ...

Answer 41

the acid dissociation constant

Question 42

pKa = ?

Answer 42

pKa = -log[Ka] (analogous to pH)

Question 43

How can pKa for weak acids be found on a titration curve?

Answer 43

It is equal to the pH value then the reaction is at 50% OH- added, the point where concentration of proton donor = proton acceptor

Question 44

What is the buffering region? Where can it be found on a titration curve?

Answer 44

It is the region where the amount of base added makes very little difference to the pH, usually surrounding the pKa point on a titration curve in the area that is mostly horizontal

Question 45

Titration ends when pH=__ and all protons are _____

Answer 45

7/converted