EXAM MODEL Q#1:
Read each problem then chose one correct answer (Notice that you should solve the problem showing each step involved and no mark will be given if you do not show the steps you used solving the problem )
1- The pH of a buffer solution containing 0.3M Tris and 0.2M Tris is :
2- The absorbance of an enzyme solution at 280nm is 0.475 , the transmittance will be :
a) 2.98 %
b) 33.49 %
3- The spectrophotometer is a device used to measure:
a) The radioactivity of a solution.
b) The conductivity of a solution.
c) The transmittance of a solution.
4- A solution containing 2g/L in a 2cm cuvette has a transmittance of 65% ,the specific absorption coefficient will be :
5- The pH of a solution obtained by adding 0.4 of solid KOH to 1.5 L of 0.002M HCL .
6- A solution containing 20g of NaCL per 200ml has a concentration of :
a) 10% w/v
b) 10 % w/w
c) 200 g/L
7- When preparing 3L of a 0.2M H2SO4 from a 5M stock solution
a) 0.12L of the stock solution is made up to 3L by distilled water.
b) 2L of the stock solution is made up to 3L by distilled water.
c) 0.83L of the stock solution is made up to 3L by distilled water.
8- If 300ml of distilled water were added to a 1L solution with a concentration of 0.5M.
a) The number of moles in the final solution decreases .
b) The number of moles in the final solution increases.
c) The number of moles in the final solution does not change
9- The wave number of 450 A is :
a) 0.22 10
b) 0.22 10
c) 0.22 10
10- The equivalant wt of a 6gm H3pO4 is :
11- A 2L solution of Fe2(SO4)3 that has an osmolarity of 0.56 is prepaerd by ;
a) Dissolving 0.56 g in 2L of distilled water.
b) Dissolving 29.8g in 2L of distilled water.
c) Dissolving 89.6g in 2L 0f distilled water
12- The concentration of a solution is :
a) Directly proportional to absorbance and inversly proportional to transmittance.
b) Directly proportional to absorbance and transmittance.
c) Directly proportional to transmittance and inversly proportional to absorbance.
Q2: Sketch the titration curve of 300ml of Lys which has a concentration of 0.1M by titrating it with 0.3M KOH show clearly how you obtained the values used to plot the curve.
pka1 = 2.18 , pka2 =8.95 , pka3= 10.53.
Q3: A solution containing NAD+ and NADH had an absorbance of 0.311 at 340nm and 1.2 at 260nm in a 1cm cuvette.calculate the concentrations of the oxidized and reduced forms of the coenzyme.
am( M-1 cm-1) for NADH NAD+are as follows;
NAD+ at 260nm = 18000 , at 340nm = 0.0
NADH at 260nm = 15000 ,at 340nm = 6220 .