Chemistry - bonds, pH, water properties

Question 1

What are the 2 types of intramolecular bonds?

Answer 1

covalent, ionic

Question 2

What are covalent bonds and the 2 types?

Answer 2

due to sharing of electrons
polar - differences in EN (H-O)
nonpolar - similarities in EN (Cl-Cl or C-H)

Question 3

What are ionic bonds?

Answer 3

electrons are not equally shared and results from direct electron transfer (ex. NaCl)
- anion and cation

Question 4

What is the difference between intermolecular and intramolecular bonds?

Answer 4

intermolecular - between molecules
intramolecular - between atoms in a molecule

Question 5

What are the 5 types of intermolecular bonds?

Answer 5

dipole-diploe, hydrogen bond, ion-dipole, van der waals, hydrophobic

Question 6

What is dipole-dipole bonds?

Answer 6

partial charges are attracted to each other, occur between polar molecules (not very strong)

Question 7

What are hydrogen bonds?

Answer 7

a strong dipole dipole bonds between H and small electronegative elements (O, N, F)

Question 8

What are ion-dipole interactions?

Answer 8

complete charge from ion reacts with a partial charge of a molecule (polar molecules)

Question 9

What are hydrophobic interactions?

Answer 9

forces that cause molecules to not want to bond with molecules other than polar molecules
ex. non-polar molecules in aqueous environments (mutual dislikes)

Question 10

What are van der waals interactions?

Answer 10

distribution of electrons asymmetrically (one side more positive one side more negative); occur when atoms and molecules are very close together

Question 11

Rank the bonds from weakest to strongest.

Answer 11

van der waals, hydrogen bonds, covalent bonds, iconic bonds

Question 12

What type of bond occurs between O and H, N and H, Na and Cl?

Answer 12

hydrogen, hydrogen, ionic

Question 13

Draw 2 molecules of water and explain how they interact with each other through hydrogen bonds.

Answer 13

The partial negative O will connect to a partial positive H of an another water molecules forming hydrogen bonds, 1 molecule can hydrogen bond with up to 4 other water molecules.

Question 14

How does hydrogen bonding account for cohesive behavior?

Answer 14

water molecules stick to each other due to hydrogen bonding; contributes to the transport of water and nutrients against gravity in plants (adhesion)

Question 15

What is surface tension and does water have high or low surface tension?

Answer 15

a measure of how difficult it is to break the surface of a liquid (due to cohesion); high - hard to break through the surface of it

Question 16

What is specific heat and does water have high or low specific heat?

Answer 16

the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1C; high - takes a lot of energy to raise the temperature

Question 17

When water absorbs heat, hydrogen bonds break/from? When hydrogen bonds form is heat absorbed/released?

Answer 17

break/released

Question 18

What is heat of vaporization and does water have high/low heat of vaporization?

Answer 18

the heat of a liquid must absorb for 1 g to be converted to gas; high - water absorbs a lot of heat causing hydrogen bonds to break and not reform (evaporate), leaving the surface cool

Question 19

Is water as a liquid more/less dense then water as a solid?

Answer 19

ice (water a as a solid) is less dense than water as a liquid; bc hydrogen bonds in ice are more ordered making ice less dense; insulate the water below

Question 20

What does it mean when we say that water is a universal solvent?

Answer 20

molecules that are polar or charged can interact with water molecules

Question 21

What does the pH of a solution depend on?

Answer 21

H+ concentration

Question 22

What is the formula to find pH/pOH and what does acids/bases/neutral mean?

Answer 22

pH + pOH = 14
acids (H+) lowers the pH
bases (OH-) raises the pH
neutral pH is seen as 7

Question 23

How do you find pH when [H+]=10^-3?

Answer 23

pH = -log[H+] -> -log[10^-3]
= -(-3)log[10]
= (3)(1) -> 3

Question 24

Distinguish between hydrophobic, hydrophilic, and amphipathic molecules, and give examples of each.

Answer 24

hydrophobic - nonpolar molecules in water; gather together and shield themselves away from water
hydrophilic - can interact with water (polar molecules)
amphipathic - contain both hydrophobic and hydrophilic parts; phospholipids

Question 25

What is the function of a buffer?

Answer 25

resist pH change upon the addition of an acidic or basic components