- Which of the following is not the application of gel filtration? (PPSC 2021)
(a) Purification
(b) Relative molecular mass determination
(c) Protein concentration
(d) None of these
Answer: (d) - Which solvent is usually used for SEC in our lab?(PPSC 2015)
(a) tetrahydrofuran
(b) toluene
(c) water
(d) None of these
Answer: (a)
Explanation
Tetrahydrofuran (THF) is one of the most commonly used solvents for non-aqueous size-exclusion chromatography (SEC) because it is a good solvent for a wide range of polymer types
THF is an aprotic solvent and cannot donate a proton for ionization. THF should be paired with a protic mobile phase (i.e. 20-50% water) when possible. The addition of 0.2% acetic acid, 0.1% formic acid or 10-20 mM NH-4OAc to the mobile phase will assist positive mode ionization. - At the same temperature, the average molar kinetic energy of N2 and CO is?
(a) KE1 > KE2
(B) KE1 = KE2
(c) KE1 < KE2
(d) None of these
Answer: (b)
Explanation
Average kinetic energy does not depend on the nature of the gas and their weight. It only depends on temperature. These same temperature condition is given. So, kinetic energies are same.
- Which law states that the volume of an ideal gas at constant pressure is directly proportional to its absolute temperature?
(a) Boyle’s law
(b) Joule’s Law
(c) Avogadro’s law
(d) Charles’s Law
Answer: (d) - Which of the following contains an atom (other than hydrogen) which lacks an octet of valence electrons? (PPSC 2020)?
(a) NH3
(b) H3O+
(c) NH4+
(d) BH3
Answer: (d) - Which isomerism is not exhibited in alkene? PPSC 2017?
(a) geometrical
(b) metamerism
(c) chain isomerism
(d) position isomerism
Answer: (b) - Which of the following is most basic? (PPSC 2021)?
(a) CH3NH2
(b) H2O
(c) NH3
(d) CH3OH
Answer: (a) - Among the following the maximum covalent character is shown by the compound. (PPSC 2020)?
(a) MgCl2
(b) FeCl2
(c) SnCl2
(d) AlCl3
Answer: (d) - What is the value of universal gas constant in Nernst equation when the potential is given in volts? (PPSC 2015)?
(a) 8.314 J mol-1K-1
(b) 0.0821 L atm mol-1K-1
(c) 8.205 m3 atm mol-1K-1
(d) 1.987 cal mol-1K-1
Answer: (a) - Which of the following is true in the case of the Zn-Cu cell? (PPSC 2020)?
(a) The flow of electrons takes place from copper to zinc
(b) E0 red of the copper electrode is less than that of a zinc electrode
(c) Zinc acts as an anode and copper as a cathode
(d) All are correct
Answer: (c) - Chromatography is a physical method that is used to separate and analyse __
(a) Simple mixtures
(b) Complex mixtures
(c) Viscous mixtures
(d)none of these
Answer: (b)
Explanation
Chromatography is a physical method that is used to separate complex mixtures. The mixture of different components is flushed through the system at different rates.
Chromatography can function as a separation technique because different components in a mixture have different attractions to the stationary and the mobile phase. The different attractions are due to the different properties of the components in the mixture.
As the complex mixture passes through the column, how fast the individual components of the mixture elute from the column will depend upon two features:
1) The extent to which each compound ‘holds on to’ the stationary phase. This depends upon interactions between the individual components and the silica gel.
2) How soluble the individual components are in the mobile phase (the eluent). This depends on the interactions between the components and the solvent system. - Which of the following is a special adsorbent used in gas-solid chromatography?
(a) Molecular sieves
(b) Silica gel
(c) Alumina
(d) None of these
Answer: (a)
Explanation
Molecular sieves are a special adsorbent used in gas-solid chromatography. It is used in open tubular columns. Molecular sieves have the ability to distinguish materials on the basis of their size. This property can be used in separating molecules of linear structure from bulky ones.
A molecular sieve is a material with pores (very small holes) of uniform size. These pore diameters are similar in size to small molecules, and thus large molecules cannot enter or be adsorbed, while smaller molecules can. As a mixture of molecules migrate through the stationary bed of porous, semi-solid substance referred to as a sieve (or matrix). - Which of the following is not a desirable feature of the ovens used in gas chromatography?
(a) It must have a fast rate of heating
(b) Power consumption should be kept low
(c) It must have maximum thermal gradients
(d) None of these
Answer: (c)
Explanation
This equilibrium has a direct impact on temperatures in gas chromatography. If the oven temperature is too cool, a compound will spend most of its time condensed in the stationary phase. Only a very small amount that can evaporate will transfer down the column.
Conversely, if the temperature is very high then the equilibrium will shift in the opposite direction. The compound will spend all of its time in the vapor phase and not condense into the stationary phase.
Gas chromatography works when a compound can transition freely both into and out of the stationary (condensed) phase. Only when the compound is condensed can it interact with the stationary phase. Only when the compound is in the vapor phase can the mobile phase push the compound along the column to the detector. - In chromatogram, the position of peaks on the time axis can be used to determine which of the following?
(a) Components of the sample
(b) Column resolution
(c) Column efficiency
(d)none of these
Answer: (a)
Explanation
Chromatogram is a detector that responds to concentration solute and is placed at the end of the column. The position of peaks on the time axis can be used to determine components of the sample.
Each peak represents a component present in the sample. Retention time is time interval between sample injection and the maximum of the peak. It is characteristic of the identity of the component under the operating conditions.
The chromatogram is a two-dimensional plot with the ordinate axis giving concentration in terms of the detector response, and the abscissa represents the time.
The detector gives a response as a peak whose height should be ideally dependent on the concentration of the particular component.
35. The correct order for the basic features of a mass spectrometer is
(a) acceleration, deflection, detection, ionization
(b) ionization, acceleration, deflection, detection
(c) acceleration, ionization, deflection, detection
(d) None of these
Answer: (b)
Explanation
The correct order for the basic features of a mass spectrometer is ionization, acceleration, deflection, and defection.
Mass spectrometry is the method in which the chemical substances are identified by sorting the gaseous ions in electric and magnetic fields which occurs during the mass to charge ratios.
- Which of the following metals does not form amalgams??
(a) Zinc
(b) Copper
(c) Iron
(d) Magnesium
Answer: (c) - Find the fraction of the total pressure exerted by hydrogen if it is mixed with ethane in an empty container at 25℃?
(a) 15/16
(b) 1/16
(c) 1/2
(d) 1
Answer: (a) - Maximum deviation from ideal gas behaviour is expected from __ gas.?
(a) CH4
(b) NH3
(c) N2
(d) None of these - The heat released at the time of condensation is called as?
(a) Sublimation heat
(b) Condensation Heat
(c) Latent Heat
(d) None of these - Which of the following is not conjugated unsaturated system.
(A) Allyl radical
(b) Allyl cation
(c) 1,3-butadiene
(d) 1-penten-4-yne
Answer: (d)
