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Knec Pharmaceutical Chemistry October/November 2008 Question Paper

Knec Pharmaceutical Chemistry October/November 2008

Course:Diploma In Pharmacy

Exam Year:2008

2421/305
PHARMACEUTICAL CHEMISTRY
Oct./Nov.2008
Time: 3 Hours

THE KENYA NATIONAL EXAMINATION COUNCIL
DIPLOMA IN PHARMACY
PHARMACEUTICAL CHEMISTRY
3 hours
INSTRUCTIONS TO CANDIDATES
You should have the following for this examination:
Answer booklet
Battery operated scientific calculator
This paper consists of TWO section;A AND B.
Answer all questions in section A and any three questions from section B.
Each question i n section A carries 4 marks while each question in section B
Carries 20 marks.
Maximum marks for each part o f a question are indicated.

SECTION A (4O MARKS)
Answer all the questions in this section.
1. Differentiate between competitive and non – competitive antagonism in a cholinergic system. (4marks)

2. Explain why amphetamine, drawn below is orally active and exhibit optical isomerism.
(4marks)

3. (a) Name three naturally occurring estrogens (3marks)

(b) State why the above compounds are not used clinically. (1 mark)

4. (a) Draw the basic structure common in most anti convulsants. (2marks)

(b) Identify the above basic structure in barbiturate and benzodiazepine structure. (2marks)

5. The structure below is of histamine neuro transmitter.

Identify and name the structure features essential for histaminic activity. (4marks)

6. 0.5 g of drug Z containing Ferrous Sulphate (FeSo₄)were dissolved in distilled water to produce 100 cm³ solution of drug in a volumetric flask.25 cm³ of the above solution reacted completely with 15.0 cm³ of 0.01M standard potassium permanganate in presence of dilute sulphuric acid . Fe =56.

( a) Write a balanced ionic equation of the reaction between ferrous ion (Fe²⁺) and manganate Mno^-₄ ions in presence of acid (1 mark)

(b) Calculate the iron content (Fe²⁺) in 0.5g of drug Z. (3marks)

7. Outline the steps involved in laboratory analysis of aspirin tablets B.P. (4marks)

8. With a suitable example in each case, explain the meaning of direct and indirect acting sympathomimetics. (4marks)

9. Define the following:

(a) Gramme equivalent weight of a dibasic acid; (2marks)
(b) A normal solution. (2marks)

10. Derive the Henderson –Hasselbalch equation pf a week base ,BoH. (4marks)

SECTION B(60 MARKS)
Answer any THREE questions from this section.
11. (a) What is a buffer solution? (2 marks)
b. Benzoic acid is a week monobasic acid. Explain how a mixture of benzoic acid and sodium benzoate can act as a buffer on addition of small amounts of either hydrochloric acid (HCL) or sodium hydroxide (NaOH) solution. (4marks )
c. 14.4gm of sodium benzoate are dissolved in 1000cm³ of 0.01m benzoic acid. Calculate the approximate pH of the resulting solution. (Given that the ka of benzoic acid = 6.3 x 10^-5 moles per litre). (4marks)

d) Define an acid and a base according to the following:
i. Arrhenius concept
ii. Lewis concept (4marks)
e) State six characteristics of an ideal antacid. (6marks)
12. (a) State FOUR ways by which radiation kills micro – organisms when used as a means of sterilization. (6marks)
b. Discuss naturally occurring penicillins under the following sub headings:
i. Stereochemistry (2 marks)
ii. Stability in acid and basic environment. (4marks)
c.State three short coming of naturally occuring penicillins. (3mark)
d. Below is the structure of chloramphenicol

State the structure activity relationship(S.A.R) of the above compound. (7marks)

13. The following is the structure of phenothiazines

a) With suitable examples, give the general structure of various phenothiazines.
(6marks)
b) Explain why promethazine has anti–histaminic activity.(3marks)
c) State two structural modifications to phenothiazines that has resulted in drugs for 1.M administration with depot effect.
(2marks)

d) State the structural changes to phenothizine ring to yield compounds with anti-depressant action.
(2marks )
e) State the structural activity relationship (S.A.R) of chlorpromazine as an anti-psychotic action.
(2marks)
14. The general structure of adrenergic sympathomimetics is given below

Outline its structure activity relationship (S.A.R). (20marks)
15. Define the following terms
(a) (i) redox titration;
(ii) gravimetry titration;
(iii) complexometric titration;
(iv)argenometry titration;
(v)titrant.
(10marks)
(b) 50.0cm³ of 0.16M aqueous potasium permanganate (an excess) were added to 25cm³ of aqeous potassium nitrate(KNO₂) in presence of dilute sulfuric acid. The excess manganate Mno^-₄ ions required 2.50 cm³ of 0.1 M ferrous (Fe²⁺) ions for complete reaction in presence of acid.

i. Calculate the concentration in moles per litre (molarity) of potasium nitrate solution.
(7marks)
ii. The concentration in grams per litre of potassium nitrite aqueous.
(3marks)

Knec Pharmaceutical Chemistry October/November 2008 Question Paper

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