Analytical Methods in Chemistry (CHMS3104)
BSc, Chemistry - CHMS
Semester: Resit
Level: 300
Year: 2018
UNIVERSITY OF BAMENDA FACULTY OF SCIENCE
RE-SIT SEMESTER EXAMINATIONS 2018
Department: chemistry Course instructors: NFOR E. Ngwang
Month: March Course code & Number: CHMS3104
Year: 2018 Course title: ANALYTICAL AND INSTRUMENTAL METHODS
Time allowed: 2 hours Credit value: 6
Instructions: ANSWER ALL QUESTIONS IN AN ORDERLY MANNER. You must show
your calculations, including equations and proper units on a question to obtain any mark.
Q1 (a) Calculate the equivalent weight and normality for a solution of 6.0 M H
3
PO
4
given the following
reactions:
(i)
H
3
PO
4
(aq) + 3OH
-
(aq) = PO
4
3-
(aq) + 3H
2
O(I)
(ii)
H
3
PO
4
(aq) + 2NH
3
(aq) = HPO
4
2-
(aq) + 2NH
4
+
(aq)
(Hi) H
3
PO
4
(aq) + F
-
(aq) = H
2
PO
4
-
(aq) + HF(aq) 3marks
(b) Commercial HCl is labelled 37% m/m with density of 1.18g/mL. Find
(i)
Molarity of HCl
(ii)
Mass of solution containing 0.1 mol of HCl.
(iii)
Volume of solution containing 0.1 mole of HCl. 6marks
(c) A concentrated solution of aqueous ammonia is 28.0% w/w NH
3
and has a density of 0.899 g/mL.
What is the molar concentration of NH
3
in this solution? 2marks
Q2 (a)By the used of equations only explain the salient features of Kjeldahl method of analysis. 4marks
(b) Briefly explain the difference between a Fajans and Volhard’s titration. 3 murks
Q3 (a) A sample has a percent transmittance of 50%. What is its absorbance? 2marks
(b) A 5.00 x 10
-4
M solution of an analyte is placed in a sample cell that has a path length of 1.00 cm.
When measured at a wavelength of490 nm, the absorbance of the solution is found to be 0.338. What is the
analyte’s molar absorptivity at this wavelength? 3marks
Q4. (a) Name two types of electrical cells define them. (4 points)
(b). You are given the following cell (10 points)
Zn(s)|Zn
2+(
aq, 0.0100 M) || Ag
+
(aq, 1.15 M) | Ag(s)
Zn
2+(
aq) + 2e →Zn(s) E° = - 0.76 V
Ag+(aq) + e →Ag(s) E° = 0.80 V
i.
Which species is oxidized when current is allowed to pass through the cell?
ii.
Which species is reduced when current is allowed to pass through the cell?
iii.
What is the value of E°
cell
?
iv.
Which electrode is the anode?
v.
In which direction do electrons flow in the external circuit?
vi.
How many electrodes are transferred in the balanced equation?
vii.
What is the value of Q, the reaction quotient for the cell?
viii.
What is the cell potential at 25 °C?
ix.
What is the value of the equilibrium constant at 25 °C for the reaction?
c) You are given the following cell: (10 points)
IO
3
-
+ 6H
2
O + 5e ⇆ 1/21
2
(
S
)
+
3H
2
O E°= 1.195 V
Br
2
(l)+2e ⇆2Br
-
E°= 1.087 V
Calculate E° and K
eqm
for the following reaction.
l
2
(s) + 5Br
2
(aq) + 6H
2
O ⇆ 2IO
3
-
+ 12H
+
+ 10Br
-
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