Chemistry - bonds, pH, water properties Flashcards
What are the 2 types of intramolecular bonds?
covalent, ionic
What are covalent bonds and the 2 types?
due to sharing of electrons
polar - differences in EN (H-O)
nonpolar - similarities in EN (Cl-Cl or C-H)
What are ionic bonds?
electrons are not equally shared and results from direct electron transfer (ex. NaCl)
- anion and cation
What is the difference between intermolecular and intramolecular bonds?
intermolecular - between molecules
intramolecular - between atoms in a molecule
What are the 5 types of intermolecular bonds?
dipole-diploe, hydrogen bond, ion-dipole, van der waals, hydrophobic
What is dipole-dipole bonds?
partial charges are attracted to each other, occur between polar molecules (not very strong)
What are hydrogen bonds?
a strong dipole dipole bonds between H and small electronegative elements (O, N, F)
What are ion-dipole interactions?
complete charge from ion reacts with a partial charge of a molecule (polar molecules)
What are hydrophobic interactions?
forces that cause molecules to not want to bond with molecules other than polar molecules
ex. non-polar molecules in aqueous environments (mutual dislikes)
What are van der waals interactions?
distribution of electrons asymmetrically (one side more positive one side more negative); occur when atoms and molecules are very close together
Rank the bonds from weakest to strongest.
van der waals, hydrogen bonds, covalent bonds, iconic bonds
What type of bond occurs between O and H, N and H, Na and Cl?
hydrogen, hydrogen, ionic
Draw 2 molecules of water and explain how they interact with each other through hydrogen bonds.
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.
How does hydrogen bonding account for cohesive behavior?
water molecules stick to each other due to hydrogen bonding; contributes to the transport of water and nutrients against gravity in plants (adhesion)
What is surface tension and does water have high or low surface tension?
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
What is specific heat and does water have high or low specific heat?
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
When water absorbs heat, hydrogen bonds break/from? When hydrogen bonds form is heat absorbed/released?
break/released
What is heat of vaporization and does water have high/low heat of vaporization?
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
Is water as a liquid more/less dense then water as a solid?
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
What does it mean when we say that water is a universal solvent?
molecules that are polar or charged can interact with water molecules
What does the pH of a solution depend on?
H+ concentration
What is the formula to find pH/pOH and what does acids/bases/neutral mean?
pH + pOH = 14
acids (H+) lowers the pH
bases (OH-) raises the pH
neutral pH is seen as 7
How do you find pH when [H+]=10^-3?
pH = -log[H+] -> -log[10^-3]
= -(-3)log[10]
= (3)(1) -> 3
Distinguish between hydrophobic, hydrophilic, and amphipathic molecules, and give examples of each.
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
What is the function of a buffer?
resist pH change upon the addition of an acidic or basic components
