Biochem Hw 1

Which of the followings are true? (MA)

A. H2O contains polar covalent bonds

 

B. H2O can disrupt hydrogen bonds formed by other molecules in aqueous solutions, basically via forming a new hydrogen bond between H2O and those molecules

 

C. Non-polar molecules can not contain polar covalent bonds

 

D. H2O has a higher boiling point than methane primarily due to formation of hydrogen bonds

A, B, D

Which of the followings are true? (MA)

 

A. Ionic interactions are weak bonds in some conditions (aqueous)

 

B. Hydrophobic interactions are caused by attraction (not Van der Waals interaction) between hydrophobic molecules

 

C. Van de Waals interactions may generate significant interactions if at a large number

 

D. Weak bonds may allow for specific interactions between molecules

A,B,D

Which of the followings are true of strong and weak acids/bases? (MA)

 

A. Weak acids, even if at higher concentrations, always generate less hydrogen ion than strong acids

 

B. Strong acids are usually completely ionized in aqueous solutions

 

C. Weak bases are usually not completely ionized in aqueous solutions

 

D. Carbonic acid (H2CO3) is a weak acid

 

E. Ammonia (NH3) is a strong base

B,C,D

Which of the followings are true of pH, pOH, and Kw? (MA)

 

A. Pure water at 25 degree and 1 atmosphere pressure is barely ionized

 

B. The higher of the pH, the higher concentration of hydrogen ion

 

C. The higher of the pOH, the higher concentration of hydrogen ion

 

D. For aqueous solution at specific temperature and atmosphere pressure, the Kw of H2O is a constant

 

E. The unit of Kw is M not M square

A,C,D

Which of the following is true in aqueous solution (this is basically a mathematical issue)? (MC)

 

A. 0.1 M HCl has a pH -1

 

B. 0.1 M acetic acid has a pH more than 1 (need to think)

 

C. 0.1 M NaOH has a pH 1

 

D. 0.2 M HCl has a higher pH than 0.1 M HCl

B

Which of the following has the strongest buffering capacity? (MC)

 

A. H2O

 

B. 0.1 M HCl

 

C. 0.1 M carbonic/bicarbonate (H2CO3/HCO3-) at pH ~pKa

 

D. 0.2 M carbonic/bicarbonate (H2CO3/HCO3-) at pH ~pKa

D

Which of the followings are usually considered as week interactions?

 

A. Ionic interaction in a salt crystal

 

B. Van der Waals interaction

 

C. Hydrogen bond

 

D. Hydrophobic interaction

 

E. Ionic interacion in water based solution

 

F. Covalent bond

B,C,D,E