Hey Guys, I am a college grad but taking a standardized exam, hence I do not have professors to go to for help. Could some one please help me with few questions?
Question 1. Which of the following is closest to the pH of a solution that contains 5 millimolar per liter of H+ ions.
A. 1.2
B. 2.3
C. 3.7
D. 6.5
E. 7.5
The answer is B, but I don't know how to calculate.
Question 2. The ionic strength of MgCl2 is
A. 0.25
B. 0.5
C. 1.0
D. 1.5
E. 5.0
The answer is D, I don't know how to do it though.
Question 3. What is the pKa of trimethylammonium in water if the base ionization constant Kb for trimethylamine is 7.4 * 19^-5? (log 7.4 * 10^-5 = -4.13)
A. -4.13
B. 2.87
C. 4.13
D. 9.87
E. 11.13
The answer is D. I don't know how to get the answer though.
Question 4. In an intact cell, the free energy change associated with an enzyme catalyzed reaction is frequently different from the standard free energy change of the same reaction because in the intact cell the
A. activation energy is different
B. reaction is always near equilibrium
C. enzyme may be regulated allosterically
D. Reactants are not at 1 M concentrations
E. Reaction may be catalyzed by more than one enzyme.
The answer is D, but can some one explain a little more?
Question 5. The pH of a 10^-4 molar HCl solution prepared with pure water at pH 7.0 is closest to.
A. 6.0
B. 6.9
C. 7.1
D. 7.9
E. 8.0
The answer is B.
The nucleoside adenosine exists in a pronated form with a pKa of 3.8. The percentage of pronated form at pH 4.8 is closest to
A. 1
B. 9
C. 50
D. 91
E. 99
The answer is B.