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BCH 371 - Exam 1 (Ch. 2-5) questions and correct answers
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BCH 371 - Exam 1 (Ch. 2-5) questions and correct answers
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BCH 371 - Exam 1 (Ch. 2-5)True or False: H-Bond is stronger when the three atoms involved in the bon lie at an angle - correct
answer ✔✔False; Hydrogen bonds are much stronger in a linear fashion - straight
How many H-bonds does water molecule make with neighboring water molecule in liquid and solid
forms? - correct answer ✔✔Liquid: watch water molecule hydrogen bonds with an average of 3.4 other
water molecules
Solid: each water molecule forms 4 hydrogen bonds - the
What are micelles? Which biomolecules are found in this form? - correct answer ✔✔High concentration
of amphipathic molecules aggregate into micelles. Phospholipids dispersed in a liquid form a colloidal
suspension
Name four types for noncovalent interaction found among biomolecules in aqueous solvents. - correct
answer ✔✔Ionic Interactions: electrostatic interactions between permanently charged species, or
between the ion and a permanent dipole.
Van der Waals: weak interactions between al atoms, regardless of polarity. Attractive (dispersions) and
repulsive (steric) component
Hydrophobic effect: complex phenomenon associated with the ordering of water molecules around
nonpolar substances
Dipole interactions: electrostatic interaction between uncharged but polar molecules
What is the concentration of -OH in a solution of 0.24M HCl? - correct answer ✔✔
, Solution A has a pH of 8 and solution B is 10^7 times more acidic than solution A. What will be the pH of
solution B? (hint: 1pH unit change = 10 times change in H+ concentration, higher H+ = lower pH) - correct
answer ✔✔
Weak acid and its conjugate base (H2PO4- / HPO4^2-) has a pKa of 6.86. What would be the best
buffering range for this?
a. pH 6-7
b. pH 8.3 - 10.3
c. pH 5.9-7.9
d. pH 4-8 - correct answer ✔✔a. pH 6-7
Work example 2-6 (a) (pg. 66) - correct answer ✔✔
End chapter problems: 11,13,14 (pg 70) - correct answer ✔✔
Hydrogen Bonds - correct answer ✔✔Are strong dipole-dipole or charge-dipole interactions that arise
between a covalently bound hydrogen and lone pair of electrons.
Typically involve two electronegative atoms (frequently nitrogen and oxygen)
Hydrogen bonds are strongest when the bonded molecules allow for linear bonding patterns (in a line)
Hydrogen bonds in water - correct answer ✔✔Water can server are both, an H donor, an H acceptor.
Hydrogen bonding in water is cooperative.
Up to four bonds per water molecule gives water its: anomalously high boiling point, anomalously high
melting point, unusually large surface tension.
Hydrogen bonds between neighboring molecules are weak, relative to the H-O covalent bonds
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