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Direction (Q. Nos. 1-12) This section contains 12 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONLY ONE option is correct.
Q. Which of the following compounds are soluble in H2O ?
All these are soluble in water due to intermolecular H-bonding.
Which of the following has maximum boiling point?
Due to intermolecular H-bonding at two terminals boiling point of glycol is maximum.
In which of the following boiling point of Column I is not higher than that of Column II?
(a) Intermolecular H-bonding, boiling point increases with molecular weight for compounds within the same family.
(b) H-bonding is absent is CH3CH2CH3.
(c) Methanol is the larger molecule but H2O has more H-bonding because of two O—H bonds.
Thus, boiling point of H2O(ll) > CH3OH(l).
(d) Molecular weight of butanol is much higher and overcomes attractive forces of butanol.
Which of the following correctly represents H-bonding?
H-bonding is between polar and electronegative 0, N and F C-atom or H attached to C is not polar. Thus, (a), (c), (d) are incorrect.
In dimer formation of which O-atom(s) is/are involved through H-bonding?
In the following compounds, select the points of interm olecular H-bonding (linear),
1. Enoiic H, acidic and polar takes part in H-bonding.
2. 3° alcohol least acidic maximum basic.
3. Carbonyl oxygen is not involved.
4. Acidic and polar H, takes part in H-bonding.
In the following alcohol, which — OH group is involved to the maximum extent in H-bonding?
O — H group is attached to (ene) is m ost a cidic and thus, has maximum intermolecular H-bonding.
Among the following sets, highest boiling points are of the species.
I. HF, HCI, HBr, HI
II. H2O, H2S, H2Se, H2Te
III. NH3,PH3, AsH3,SbH3
F, O and N are electronegative elements. Thus, HF molecules are associated by intermolecules H-bonding giving it a liquid state and thus highest boiling point out of HF, HCl.HBr and HI.
Similarly, H2O has highest boiling point, and NH3 has highest boiling point.
The H-bond is shortest in
(EN) of S < 0 < F
Thus, H is attracted to larger extent by F atom making (H.......F) bond shortest.
What is the dominant intermolecular force or bond that must be overcome in converting liquid CH3CH2OH to vapours?
CH3CH2OH is in liquid state due to association as a result of intermolecular H-bonding.
Number of water molecules directly attached to one water molecule is
One water molecule is directly attached to four water molecules. Thus, coordination number of water is 4.
Consider the following compounds
H-bonding is not present in
HCI: EN of Cl is smaller, hence less polar than HF.
CH3COO- : H attached to C-atom is non-polar hence
HCI, CH4, CH3COO- — lack H-bonding.
Direction (Q. Nos. 13-16) This section contains 4 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THANT ONE is correct.
In which of the following I is more volatile than II?
I. Intermolecular H-bonding makes boiling point higher than that of I. Thus, I is more volatile
II. Ortho nitrophenol is more volatile than para nitrophenol because O-Nitrophenol has intramolecular hydrogen bonding whereas para nitrophenol has inter molecular H bonding and so boils relatively at higher temperature
(c) BP of H2O > > H2S
(d) BP of CH3CH2OH (due to H-bonding) > > CH3— O — CH3
Hydrogen bonding plays a central role in the following phenomenon
[JEE Advanced 2014]
(a) When liquid water changes to ice, there is an air gap inside the cage formed due to intermolecular H-bonding. Thus, volume of ice > volume of water.
Hence, density (ice) < density (water).
Thus, ice floats on water - hydrogen bonding plays its role.
(b) In gaseous phase, basicity of 1° < 2° < 3° amines due to increase of electron density at N-atom
But in aqueous (H2O) solvent, RNH2 is stabilised by solvation. Thus 1° amine is more
basic than 3° amine (3° < 1° < 2°) amines.
(c) l+ (positive inductive effect) explains this
Dimer due to intermolecular H- bonding.
Which of the following molecules are stabilised by intramolecular H-bonding?
(a) intramolecular H-bonding.
Q. unstable compound is/are
I. CCI3CH (OH)2 with two — OH groups on same carbon atom is stable due to intramolecular H-bonding.
Direction (Q. Nos. 17) Choice the correct combination of elements and column I and coloumn II are given as option (a), (b), (c) and (d), out of which ONE option is correct.
Q. Match the species in Column I with rank order of their boiling point in Column II. (Species with lowest boiling points is at SN1).
n-butane lacks H-bonding. Hence, its boiling point is least.
due to difference in polar H+ for H-bonding.
Boiling point of CH3CH2CH2CH2OH > H2O due to much larger size of alcohol.