Describe the hybridisation in case of PCl5. Why are the axial bonds longer as compared to equatorial bonds?
The ground state E.C. and the excited state E.C. of phosphorus are represented as:
The one s, three-p and one d-orbitals hybridise to yield five sets of SP3 d hybrid orbitals which are directed towards the five corners of a trigonal bipyramidal as in Fig.
Because axial bond pairs suffer more repulsive interaction from the equatorial bond pairs, therefore axial bonds have been found to be slightly longer and hence slightly weaker than equatorial bonds.
Elements X, Y and Z have 4, 5 and 7 valence electrons respectively, (i) Write the molecular formula of the compounds formed by these elements individually with hydrogen, (ii) Which of these compounds will have the highest dipole moment?
Briefly describe the valence bond theory of covalent bond formation by taking an example of hydrogen. How can you interpret energy changes taking place in the formation of dihydrogen?
What is the effect of the following processes on the bond order in N-, and 02?
(i) N2 → N+2 + e– (ii) 02 → O+2 + e–
Which of the following statements are not correct?
(a) NaCl being an ionic compound is a good conductor of electricity in the solid state.
(b) In canonical structures there is a difference in the arrangement of atoms.
(c) Hybrid orbitals form stronger bonds than pure orbitals.
(d) VSEPR theory can explain the square planar geometry of XeF4.
Match the items given in Column I with examples given in Column II.
| Column I | Column II |
| (i) Hydrogen bond | (a) C |
| (ii) Resonance | (b) LiF |
| (iii) Ionic solid | (c) H2 |
| (iv) Covalent solid | (d) HF |
| (e) 03 |
Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in C2 H4 and C2 H2 molecules.
Structures of molecules of two compounds are given below:
(a) Which of the two compounds will have intermolccular hydrogen bonding and which compound is expected to show intramolecular hydrogen bonding?
(b) The melting point of a compound depends on. among other things, the extent of hydrogen bonding. On this basis explain which of the above two compounds will show higher melting point.
(c) Solubility of compounds in water depends on power to form hydrogen bonds with water. Which of the above compounds will form hydrogen bond with water easily and be more soluble in it?
Is there any change in the hybridisation ofB and N atoms as a result of the following reaction ? BF3 + NH3 ——-> F3 B.NH3
Diamagnetic species are those which contain no unpaired electrons. Which among the following are diamagnetic?
(a) N2
(b) N22-
(c) 02
(d) o22-
Write Lewis structure of the following compounds and show formal charge on each atom. HN03, No2, H2so4
(a) How many a and n bonds are present in
(b) Why Hf is more stable than H2?
(c) Why is B2 molecule paramagnetic?
Using molecular orbital theory, compare the bond energy and magnetic character of 0+2 and O–2
What is the total number of sigma and pi bonds in the following molecules?
(a) C2 H2 (b) C2 H4
The skeletal structure of CH3COOH as shown below is correct, but some of the bonds are shown incorrectly. Write the correct Lewis structure for acetic acid.
Which molecule/ion out of the following does not contain unpaired electrons?
(a) N+2
(b) 02
(c) O22-
(d) B2
In which of the following molecule/ion all the bonds are not equal?
(a) XeF4
(b) BF–4
(c) C2H4
(d) SiF4
Predict the shapes of the following molecules on the basis of hybridization. BC13, ch4, co2, nh3
Assertion (A): Though the central atom of both NH3 and H20 molecules are sp3 hybridised, yet H – N – H bond angle is greater than that of H – O – H.
Reason (R): This is because nitrogen atom has one lone pair and oxygen atom has two lone pairs.
(a) A and R both are correct, and R is the correct explanation of A.
(b) A and R both are correct, but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A and R both are false.
Use Lewis symbols to show electron transfer between the following atoms to form cations and anions (a) K and S (b) Ca and O (c) Al and N.
Arrange the bonds in order of increasing ionic character in the molecules: LiF, K2O, N2, SO2 and ClF3.
Explain why BeH2 molecule has a zero dipole moment although the Be—H bonds are polar.
In N0–3 ion, the number of bond pairs and lone pairs of electrons on nitrogen atom are
(a) 2, 2 (b) 3, 1 (c) 1,3 (d) 4, 0
Explain the non linear shape of H2S and non planar shape of PCl3 using valence shell electron pair repulsion theory.
Give reasons for the following: ‘
(a) Covalent bonds are directional bonds while ionic bonds are non- directional.
(b) Water molecule has bent structure whereas carbon dioxide molecule is linear.
(c) Ethyne molecule is linear.
Match the species in Column I with the bond order in Column II.
| Column I | , . Column II |
| (i) NO | (a) 1.5 |
| (ii) CO | (b) 2.0 |
| (iii) o–2 | (c) 2.5 |
| (iv) 02 | (d) 3.0 |
3PO3 can be represented by structures 1 and 2 shown below. Can these two structures be taken as the canonical forms of the resonance hybrid representing H3PO3? If not, give reasons for the same.
