Group 18 elements are called noble gases and not inert gases because compounds of Kr, Xe and Rn have been prepared. Their general electronic configuration is \(ns^2\)\(np^6\) except He(\(1s^2\) ). They have highest ionisation enthalpy and positive electron gain enthalpy due to stable electronic configuration. Helium is found in sun and stars. Noble gases have low boiling points due to weak van der Waals’ forces of attraction. Xenon forms \(XeF_2\), \(XeF_4\), \(XeF_6\), \(XeOF_4\), \(XeO_3\), \(XeO_2\)\(F_2\), their structures can be drawn on bases of VSEPR theory. Helium is mixed with oxygen by deep sea divers to avoid pain. Neon is used in coloured advertising lights. Argon is used in bulbs as inert gas. Kr and Xe are used in high efficiency lamps, head light of cars. Radon is radioactive formed by a-decay of Radium 226 88Ra Argon is most abundant (0.9%) noble gas in atmosphere.
The following questions are multiple choice questions. Choose the most appropriate answer.
1) What are the elements in group 18 (the far right) of the periodic table called?
a) Alkali metals
b) Alkaline earth metals
c) Halogens
d) Noble gases
2) Out of (i) \(XeO_3\) (ii) \(XeOF_4\) and (iii) \(XeF_6\) , the molecules having the same number of lone pairs on Xe are -
a) (i) and (ii) only
b) (i) and (iii) only
c) (ii) and (iii) only
d) (i) , (ii) and (iii)
3) Which one has linear shape?
a) \(XeF_2\)
b) \(XeF_4\)
c) \(XeF_6\)
d) \(XeO_3\)
4) Which of the outer electronic configuration represent Argon?
a) \(ns^2\)\(np^4\)
b) \(ns^2\)\(np^3\)
c) \(ns^2\)\(np^6\)
d) \(ns^1\)\(np^6\)
5) Which of the following statement is false?
a) Radon is obtained from the decay of radium
b) Helium is an inert gas
c) Xenon is the most reactive among the rare gases
d) The most abundant rare gas found in the atmosphere is helium
The following questions are multiple choice questions. Choose the most appropriate answer.
1) What are the elements in group 18 (the far right) of the periodic table called?
a) Alkali metals
b) Alkaline earth metals
c) Halogens
d) Noble gases
2) Out of (i) \(XeO_3\) (ii) \(XeOF_4\) and (iii) \(XeF_6\) , the molecules having the same number of lone pairs on Xe are -
a) (i) and (ii) only
b) (i) and (iii) only
c) (ii) and (iii) only
d) (i) , (ii) and (iii)
3) Which one has linear shape?
a) \(XeF_2\)
b) \(XeF_4\)
c) \(XeF_6\)
d) \(XeO_3\)
4) Which of the outer electronic configuration represent Argon?
a) \(ns^2\)\(np^4\)
b) \(ns^2\)\(np^3\)
c) \(ns^2\)\(np^6\)
d) \(ns^1\)\(np^6\)
5) Which of the following statement is false?
a) Radon is obtained from the decay of radium
b) Helium is an inert gas
c) Xenon is the most reactive among the rare gases
d) The most abundant rare gas found in the atmosphere is helium
1) d) Noble gases
2) d) (i) , (ii) and (iii)
3) a) \(XeF_2\)
4) c) \(ns^2\)\(np^6\)
5) d) The most abundant rare gas found in the atmosphere is helium
2) d) (i) , (ii) and (iii)
3) a) \(XeF_2\)
4) c) \(ns^2\)\(np^6\)
5) d) The most abundant rare gas found in the atmosphere is helium
Group 16 elements are called chalcogens i.e., ore forming elements (oxygen, sulphur, selenium etc.) because most of the ores are oxides and sulphides. Oxygen is gas where as other elements of group 16 are solids. Oxygen shows anomalous behaviour. Oxygen is diatomic where is sulphur exists as \(S_8\) which has crown shaped structure. It shows allotropy. Sulphur is present in onion and garlic that is why they have pungent smell. Sulphur is used for manufacture of sulphuric acid which is called ‘King of chemicals’, used in fertilizer, detergents, dyes and drugs.
The following questions are multiple choice questions. Choose the most appropriate answer.
1) Group 16 elements are also known as
a) Noble elements
b) Halogens
c) Pnictogens
d) Chalcogens
2) Acidic character of hydrides of group 16 elements is in the order
a) \(H_2\)O < \(H_2\)S < \(H_2\)Se < \(H_2\)Te
b) \(H_2\)S < \(H_2\)Se < \(H_2\)Te < \(H_2\)O
c) \(H_2\)O < \(H_2\)Se < \(H_2\)Te < \(H_2\)S
d) \(H_2\)O < \(H_2\)S < \(H_2\)Te < \(H_2\)Se
3) Hybridisation of S in \(SF_4\) and geometry of \(SF_4\) are respectively
a) \(sp^3\)d, trigonal pyramidal
b) \(sp^3\)d, see saw
c) \(sp^3\), tetrahedral
d) \(dsp^2\), square planner
4) Which is not an acidic oxide?
a) \(CO_2\)
b) \(SO_2\)
c) \(Na_2\)O
d) \(Cl_2\)\(O_7\)
5) Which is not correct about allotropes of sulphur
a) The stable form at room temperature is rhombic sulphur
b) Monoclinic sulphur is stable above 369 K and transforms into rhombic sulphur below it
c) At 369 K both the forms are stable
d) Monoclinic sulphur is soluble in \(CS_2\) while rhombic sulphur not
Assertion :- Interhalogen compounds are more reactive than halogen.
Reason :- They all undergo hydrolysis giving halide, cation derived from the smaller halogen & anion derived from larger halogen.
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.
Assertion:-The stability of hydrides decreases from \(NH_3\) to \(BiH_3\).
Reason:-There is a decrease in bond dissociation enthalpy of bond E-H from \(NH_3\) to \(BiH_3\). (E=Element of group 15)
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.
Assertion :-Solubility of noble gases in water decreases with increasing size of the noble gases.
Reason :- Solubility of noble gases in water is due to dipole- dipole interaction.
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.
Assertion :- Nitrogen has higher ionisation enthalpy than that of oxygen.
Reason :- Nitrogen has smaller atomic size than that of Oxygen.
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.
Assertion:-Nitrogen is restricted to a maximum covalency of 4.
Reason:-Nitrogen exists as a diatomic molecule (\(N_2\)) with a triple bond.
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.
Assertion:- \(H_2\)O is the only hydrides of the Chalcogens which is liquid.
Reason :- In ice each O atom is surrounded by 4H-atom.
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.
Read the passage given below and answer the following questions:
Nucleophilic substitution reactions are of two types; substitution nucleophilic bimolecular (SN2) and substitution nucleophilic unimolecular (SN1) depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards SN1 and SN2 reactions depends on various factors such as steric hindrance, stability of intermediate or transition state and polarity of solvent. SN2 reaction mechanism is favoured mostly by primary alkyl halide or transition state and polarity of solvent, SN2 reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of SN1 reactions.
(i) Which of the following is most reactive towards nucleophilic substitution reaction?
(a) \(C_6\)\(H_5\)Cl
(b) \(CH_2\)=CHCl
(c) \(ClCH_2\)\(CH=CH_2\)
(d) \(CH_3\)CH=CHCl
(ii) Isopropyl chloride undergoes hydrolysis by
(a) SN1 mechanism
(b) SN2 mechanism
(c) SN1 and SN2 mechanism
(d) neither SN1 nor SN2 mechanism
(iii) Tertiary alkyl halides are practically inert to substitution by SN2 mechanism because of
(a) insolubility
(b) instability
(c) inductive effect
(d) steric hindrance
(iv) Which of the following is the correct order of decreasing SN2 reactivity?
(a) \(RCH_2\)X > \(R_2\)CHX > \(R_3\)CX
(b) \(R_3\)CX > \(R_2\)CHX > \(RCH_2\)X
(c) \(R_2\)CHX > \(R_3\)CX > \(RCH_2\)X
(d) \(RCH_2\)X > \(R_3\)CX > \(R_2\)CHX
(v) An organic molecule necessarily shows optical activity if it-
a) contains asymmetric carbon atoms
b) is non-polar
c) is non-superimposable on its mirror image
d) is superimposable on its mirror image
Read the passage given below and answer the following questions:
The replacement of hydrogen atom in a hydrocarbon, aliphatic or aromatic results in the formation of haloalkanes and haloarenes respectively. Haloalkanes contain halogen atom attached to \(sp^3\) hybridised carbon atom of an alkyl group whereas haloarenes contain halogen atom attached to \(sp^2\) hybridised carbon atom of an aryl group. Haloalkanes and haloarenes may be classified on the basis of number of halogen atoms in their structures as mono, di or poly halogen compounds and also on the basis of the state of hybridisation of carbon atom to which the halogen atom is bonded.
(i) Which of the following halide is 2°?
(a) Isopropyl chloride
(b) Isobutyl chloride
(c) n-propyl chloride
(d) n-butyl chloride
(ii) Which of the following is a Gem-dibromide is :
(a) \(CH_3\)\(CH(Br)CH_2\)(Br)
(b) \(CH_3\)\(CBr_2\)\(CH_3\)
(c) \(CH_2\)\((Br)CH_2\)\(CH_2\)
(d) \(CH_2\)\(BrCH_2\)Br
(iii) IUPAC name of (\({\\(CH_3\\)}_3\))CCl is:
(a) 3-Chlorobutane
(b) 2-Chloro-2-methylpropane
(c) t-butyl chloride
(d) n-butyl chloride
(iv) Which of the following is a primary halide?
(a) Isopropyl iodide
(b) Secondary butyl iodide
(c) Tertiarybutylbromide
(d) Neohexylchloride
(v) Which one of the following is not an allylic halide?
(a) 4-Bromopent-2-ene
(b) 3-Bromo-2-methylbut-1-ene
(c) 1-Bromobut-2-ene
(d) 4-Bromobut-1-ene
The sequence of bases along the DNA and RNA chain establishes its primary structure which controls the specific properties of the nucleic acid. An RNA molecule is usually a single chain of ribose-containing nucleotide. On the basis of X-ray analysis of DNA, J.D., Watson and F.H.C. CYST (shared noble prize in 1962) proposed a three dimensional secondary structure for DNA. DNA molecule is a long and highly complex, spirally twisted, double helix, ladder like structure. The two polynucleotide chains or strands are linked up by hydrogen bonding between the nitrogenous base molecules of their nucleotide monomers. Adenine (purine) always links with thymine (pyrimidine) with the help of two hydrogen bonds and guanine (purine) with cytosine (pyrimidine) with the help of three hydrogen bonds. Hence, the two strands extend in opposite directions, i.e., are
antiparallel and complimentary.
In these questions (Q. No. i-iv), a statement of assertion followed by a statement of reason is given.
Choose the correct answer out of the following choices.
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. c) Assertion is correct statement but reason is wrong statement
d) Assertion is wrong statement but reason is correct statement.
i) Assertion - DNA molecules and RNA molecules are found in the nucleus of a cell.
Reason : There are two types of nitrogenous bases, purines and pyrimidines. Adenine (A) and guanine (G)are substituted purines; cytokine (C), thymine (T) arid uracil (U) are substituted pyrimidines.
ii) Assertion .- In both DNA and RNA, heterocyclic base and phosphate ester linkages are at C- 1’ and C-5’respectively of the sugar molecule.
Reason : Nucleotides and nucleosides mainly differ from each other in presence of phosphate units.
iii)Assertion .- The backbone of RNA molecule is a linear chain consisting of an alternating units of heterocylic base, D-ribose and a phosphate.
Reason : The segment of RNA which acts as the instruction manual for the synthesis of protein is ribose.
iv) Assertion.- In DNA, the complementary bases are, adenine and guanine; thymine and cytosine.
Reason : The phenomenon of mutation is chemical change in DNA molecule.
The solubility of gases increases with increase of pressure. William Henry made a systematic investigation of the solubility of a gas in a liquid. According to Henry’s law “the mass of a gas dissolved per unit volume of the solvent at constant temperature is directly proportional to the pressure of the gas in equilibrium with the solution”. Dalton during the same period also concluded independently that the solubility of a gas in a liquid solution depends upon the partial pressure of the gas. If we use the mole fraction of gas in the solution as a measure of its solubility, then Henry’s law can be modified as “the partial pressure of the gas in the vapour phase is directly proportional to the mole fraction of the gas in the solution”.
Answer the following MCQs by choosing the most appropriate options:
(i) Henry’s law constant for the solubility of methane in benzene at 298 K is 4.27 × \(10^5\) mm Hg. The solubility of methane in benzene at 298 K under 760 mm Hg is
(a) 4.27 × \(10^{-5}\)
(b) 1.78 × \(10^{-3}\)
(c) 4.27 × \(10^{-3}\)
(d) 1.78 × \(10^{-3}\)
(ii) The partial pressure of ethane over a saturated solution containing 6.56 × \(10^{-2}\) g of ethane is 1 bar. If the solution contains 5.00 × \(10^{-2}\) g of ethane then what will be the partial pressure (in bar) of the gas?
(a) 0.762
(b) 1.312
(c) 3.81
(d) 5.0
(iii) KH (K bar) values for Ar(g), \(CO_2\)(g), HCHO(g) and \(CH_4\)(g) are 40.39, 1.67, 1.83 × \(10^{-5}\) and 0.413 respectively. Arrange these gases in the order of their increasing solubility.
(a) HCHO < \(CH_4\) < \(CO_2\) < Ar
(b) HCHO < \(CO_2\) < \(CH_4\) < Ar
(c) Ar < \(CO_2\) < \(CH_4\) < HCHO
(d) Ar < \(CH_4\) < \(CO_2\) < HCHO
(iv) When a gas is bubbled through water at 298 K, a very dilute solution of the gas is obtained. Henry’s law constant for the gas at 298 K is 150 K bar. If the gas exerts a partial pressure of 2 bar, the number of millimoles of the gas dissolved in 1 L of water is
(a) 0.55
(b) 0.87
(c) 0.37
(d) 0.66
The properties of the solutions which depend only on the number of solute particles but not on the nature of the solute are called colligative properties. Relative lowering in vapour pressure is also an example of colligative properties. For an experiment, sugar solution is prepared for which lowering in vapour pressure was found to be 0.061 mm of Hg.(vapour pressure of water at \(20^\circ\)C is 17.5 mm of Hg).
Answer the following MCQs by choosing the most appropriate options:
(i) Relative lowering of vapour pressure for the given solution is-
(a) 0.00348
(b) 0.061
(c) 0.122
(d) 1.75
(ii) The vapour pressure (mm of Hg) of Solution will be
(a) 17.5
(b) 0.61
(c) 17.439
(d) 0.00348
(iii) Mole fraction of sugar in the solution is
(a) 0.00348
(b) 0.9965
(c) 0.061
(d) 1.75
(iv) If weight of sugar taken is 5 g in 108 g of water then molar mass of sugar will be
(a) 358
(b) 120
(c) 240
(d) 400
(v) The vapour pressure (mm of Hg) of water at 293 K when 25 g of glucose is dissolved in 450 g of water is
(a) 17.2
(b) 17.4
(c) 17.120
(d) 17.02
Read the passage given below and answer the following questions:
When a protein in its native form, is subjected to physical changes like change in temperature or chemical changes like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of protein.
The denaturation causes change in secondary ann tertiary structures but primary structures remain intact. Examples of denaturation of protein are coagulation of egg white on boiling, curdling of milk, formation of cheese when an acid is added to milk.
Choose the most appropriate answer:
i) Mark the wrong statement about denaturation of proteins.
a) The primary structure of the protein does not change.
b) Globular proteins are converted into fibrous proteins.
c) Fibrous proteins are converted into globular proteins.
d) The biological activity of the protein is destroyed.
ii) Which structure{s) of proteins remains(s) intact during denaturation process?
(a) Both secondary and tertiary structures
(b) Primary structure only
(c) Secondary structure only
(d) Tertiary structure only
iii) a-helix a n d β - pleated structures of proteins are classified as
(a) primary structure
(b) secondary structure
(c) tertiary structure
(d) quaternary structure.
(iv) Secondary structure of protein refers to
a) mainly denatured proteins and structure of prosthetic groups.
b) three-dimensional structure, especially the bend between. amino acid residues that are distant from each other in the polypeptide chain.
c) linear sequence of amino acid residues in the polypeptide chain.
d) regular folding patterns of continuous portions of the polypeptide chain.
An organic compound A having molecular formula \(C_6\)\(H_6\)O turn blue litmus solution into red but does not react with sodium bicarbonate, but when treated with bromine water then form a white ppt of compound B. when compound A react with chloroform in presence of aqueous caustic soda solution at 340K then form two compound C and D. When compound A treated with caustic soda then form compound E compound E when treated with methyl halide then form compound F.
Read the above passage carefully and answer the following questions:
(i) The name of compound is:
(a) 2-methyl propene-2-ol
(b) 2-methyl phenol
(c) 2,4,6-tribromophenol
(d) Butane 1-ol
(ii) Which are isomers of each other
(a) A and C
(b) B and C
(c) C and D
(d) D and E
(iii) The IUPAC name of compound F is
(a) Anisole
(b) Methoxybenzene
(c) Salicylaldehyde
(d) 2-methyl propene-2-ol
(iv) When compound E treated with ethyl iodide then ...... form.
(a) Ehoxybenzene
(b) Ethoxy hexane
(c) Propoxypropane
(d) Benzaldehyde
(v) On oxidation with sodium dichromate and conc \(H_2\)\(SO_4\) phenol gives
(a) Benzaldehyde
(b) p-Benzoquinone
(c) o-Benzoquinone
(d) m-benzoquinone