Biochem Lab

Question 1

Which of the following concentrations is the same as 6 x 10-4M?
A. 0.6mM
B. 60 x 10-3 M
C. 6000 x 10-3 mM
D. 0.6 x 10-5 M
E. 6mM

Answer 1

A. 0.6 mM

Question 2

How many millimoles of magnesium chloride are there in 4 litres of 0.2M Mg Cl2?
A. 0.002 mmoles
B. 0.008 mmoles
C. 8 mmoles
D. 800 mmoles

Answer 2

D. 800 mmoles

Mole= mass/min

C=n/v
0.2=n/4
0.8 mol

Question 3

In an experiment a biochemist mixes 20mL of a 0.6mM solution of Ascorbic acid with a 100mL of water giving a total volume of 120mL. What is the new concentration of Ascorbic acid?
A. 0.05mM
B. 0.1mM
C. 0.12mM
D. 3.0mM

Answer 3

B. 0.1mM

C1v1=c2v2
(0.6mM)(20mL)=c2(100mL)

Question 4

In a solution the [H+]=1.3 x 10-5M. The pH of the solution is _______.
A. 1.3
B. 2.8
C. 3.6
D.4.9
E. 9.1

Answer 4

D. 4.9

PH=-log[H+]

Question 5

Which pair below is a conjugate acid/conjugate base pair?
A. H3PO4
B. NaH2PO4 and Na2HPO4
C. H3PO4 and NaOH
D. Na3PO4 and NaOH
E. H3PO4 and Na3PO4

Answer 5

B. NaH2PO4 and Na2HPO4

Question 6

A buffer is made from equal amounts of 0.2 NaHCO3 and 0.2M Na2CO3. What is its pH? (PKa’s=3.8 and 10.2)
A. 3.8
B. 5.2
C. 6.4
D. 7.0
E. 10.2

Answer 6

E. 10.2

PH= 10.2 + log (0.2/0.2)

Question 7

A student prepares 200 ml of a 0.5M phosphate buffer at pH= 6.4. What will the pH be if the student dilutes this buffer to 1 liter?
A. 3.4
B. 6.0
C. 6.4
D. 7.4
E. 11.4

Answer 7

C. 6.4

Question 8

If [HA] is greater that [A-], the pH is:
A. Below 7
B. Below the pKa
C. Equal to the pKa
D. Above the pKa
E. Above 7

Answer 8

B. Below the pKa

Question 9

What is the net charge of lysine at pH= 13? (The pKas of lysine are 2.2, 9.2 and 10.8)
A. -2
B. -1
C. 0
D. 1
E. 2

Answer 9

B. -1

Question 10

How would you describe the side chain (R group) for the amino acid valine?
A. Positively charged
B. Negatively charged
C. Non-polar
D. Polar

Answer 10

C. Non-polar

Question 11

In a paper chromatography method, leucine dissolved more in the mobile phase than is histidine. Which one will move father in a given time period?
A. Leucine
B. Histidine
C. Neither as they will move the same distance

Answer 11

A. Leucine

Question 12

Which of the following is used for color development of amino acids after separation by paper chromatography?
A. Resorcinol reagent
B. Drabkin’s reagent
C. Ninhydrin
D. DCPIP

Answer 12

C. Ninhydrin

Question 13

In a certain chromatography system isoleucine has an Rf=0.4. If the solvent travels 20cm, how far will the isoleucine travel?
A. 0.4cm
B. 4cm
C. 8cm
D. 20.4cm

Answer 13

C. 8cm

0.4=sol/20

Question 14

A cobalt chloride solution was prepared so that it had an absorbance of 0.60. Five mL of that solution was iced with ten ml of distilled water giving a total volume of fifteen ml. What was the new absorbance?
A. 0.20
B. 0.30
C. 0.40
D. 0.45
E. 0.90

Answer 14

A. 0.20

0.60 (5) = x (15)