DI-DCO Solved Exam Paper with Explanation (RAJASTHAN) . 2012 Part-5

Q.51 Sedimentation rate of suspension is studied by

a) Boyal’s law     b) Fick’s law     c) Stoke’s law      d) Dalton’s law

Ans 51. C 

A number of factors can be adjusted to enhance the physical stability of a suspension, including the diameter of the particles and the density and viscosity of the medium.

 

Limitation Of Stoke’s Equation

Stoke’s equation applies only to:
·Spherical particles in a very dilute suspension (0.5 to 2 gm per 100 ml).
·Particles which freely settle without interference with one another (without collision).
·Particles with no physical or chemical attraction or affinity with the dispersion medium.
But most of pharmaceutical suspension formulation has conc. 5%, 10%, or higher
percentage, so there occurs hindrance in particle settling.
  

Q.52 Multi point viscometer that is used to determine viscosity

a) Ostwald Viscometer                        b) Capillary Viscometer         

c) Falling ball Viscometer                   d) Cup and Bob Viscometer

Ans 52. D 

Multi point viscometers (Rotational) Cup & bob viscometers Principle: In which, the sample is sheared in space between the outer wall of a bob & inner wall of a cup into which the bob is fits. Now, either the bob or cup is made to rotate and torque resulting from viscous drag is measured by spring or sensor in the drive of the bob. The no. of rpm & torque showing rate of shear and stress resp.

Q.53 To study the stress and rate of shear, the phenomenon of converting gel to sol is known as

a) Plastic flow                         b) Pseudo plastic flow     

c) Thixotropy                           d) Dilatant flow

Ans 53. B Thixotropy is a shear thinning property. Certain gels or fluids that are thick (viscous) under static conditions will flow (become thin, less viscous) over time when shaken, agitated, or otherwise stressed. They then take a fixed time to return to a more viscous state. In more technical language: some non-Newtonian pseudoplastic fluids show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower its viscosity. A thixotropic fluid is a fluid which takes a finite time to attain equilibrium viscosity when introduced to a step change in shear rate. Some thixotropic fluids return to a gel state almost instantly, such as ketchup, and are called pseudoplastic fluids. Others such as yogurt take much longer and can become nearly solid over a duration of time. Many gels and colloids are thixotropic materials, exhibiting a stable form at rest but becoming fluid when agitated.

Q.54 What is pore size in membrane filter?

a) 0.5 µm          b) 0.22 µm         c) 0.45 µm                  d) 0.1 µm

Ans 54. B 

Q.55 Exotoxins are

a) are pyrogens   

b) are water solble and can pass through proteinous layer

c) are lipopolysachharide, protein        

d) are much less toxic to endotoxin

Ans 55. B

An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell.

Most exotoxins can be destroyed by heating. They may exert their effect locally or produce systemic effects. Well-known exotoxins include the botulinum toxin produced by Clostridium botulinum and the Corynebacterium diphtheriae exotoxin, which is produced during life-threatening symptoms of diphtheria.

Exotoxins are susceptible to antibodies produced by the immune system, but many exotoxins are so toxic that they may be fatal to the host before the immune system has a chance to mount defenses against it.

Q.56 Cetrimide is

a) Cationic surfactant                    b) Anionic surfactant

c) Nonionic surfactant                   d) Amphiophilic surfactant

Ans 56. A Cetrimide is an antiseptic which is mixture of different quaternary ammonium salts including Cetrimonium bromide (CTAB).Cetrimonium bromide ((C₁₆H₃₃)N(CH₃)₃Br, cetyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, CTAB) is one of the components of the topical antiseptic cetrimide. The cetrimonium (or hexadecyltrimethylammonium) cation is an effective antiseptic agent against bacteria and fungi.

It is a cationic surfactant. Its uses include providing a buffer solution for the extraction of DNA. It has been widely used in synthesis of gold nanoparticles (e.g., spheres, rods, bipyramids). It is also widely used in hair conditioning products.

Q.57 Smallest size of capsule most widely used is

a) 0               b) 5                              c) 1                              d) 000

Ans 57. B   

Empty hard-shell capsules are available in sizes that range from the largest size, 000, to the smallest size, 5. Larger bolus capsule shells are also available for veterinary use in large animals.

1. Size 00 (double zero) is usually the largest capsule size used orally for humans. For some patients, even size 00 capsules are too large to swallow.
2. Size 000 (triple zero) capsules are sometimes used to encapsulate medication for rectal or vaginal use. The capsule is then used like a suppository. The capsule should be moistened with lubricating jelly or water before insertion.

Q.58 Homologous series in hydrocarbons are determined by

a) Rf Value                 b) Rx Value                 c) Rm Value                d) Rt Value

Ans 58. A  In chromatography Rf  (retardation factor )= (height or length the component travelled or eluted from the starting point) divided by the total length the mobile phase or solvent travelled, mainly used in TLC (thin layer chromatography), but for LC (liquid chromatography) the Rf under standard conditions of say standard, fixed mobile phase, fixed rate of solvent, fixed stationary phase e.g rate in mls/minute, then its the time in mins or hours, that the component eluted from the starting point.

The relative rates of migration of compound are measured by Rf values (Rate of Flow):

Rf=distance compound migrated / distance solvent travelled from the origin

Q.59 Sodium methoxide is standardized by

a) Oxallic acid             b) Perchloric acid        c) Acetic acid              d) Benzoic acid

Ans 59. D Standardization of 0.1 N sodium methoxide : 400mg of the  benzoic acid is dissolved in the 80 ml of dimethylformamide and little quantity of thymolphthalein is added as indicator.

The resulting solution is titrated with the 0.1 N sodium methoxide until blue colour is obtained.

1 ml of 0.1 N sodium methoxide = 0.01221 g of benzoic acid

Q.60 Which of the following is used reference in Electron Spin Resonance?

a) Tetra methyl silane                                  b) Dimethyl formamide

 c) Diphenylpicrylhydrazyl (DPPH)            d) Trimethyl silane

Ans 60. C  DPPH is a common abbreviation for an organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored crystalline powder composed of stable free-radical molecules. DPPH has two major applications, both in laboratory research: one is a monitor of chemical reactions involving radicals, most notably it is a common antioxidant assay,and another is a standard of the position and intensity of electron paramagnetic resonance signals