Chemical Bonding and Molecular Structure quiz

The shape of the NH3 molecule is:

The hybridisation of carbon in CH4 is:

Which of these molecules has zero dipole moment?

The bond order of N2 is:

Which molecule is paramagnetic?

The shape of SF6 is:

Which of these has an incomplete octet?

The bond angle in water is about:

The number of sigma and pi bonds in ethyne (C2H2) is:

Which of these molecules shows intramolecular hydrogen bonding?

Write the Lewis dot structures of N2 and CO2. (2 marks)

Why is the bond enthalpy of a single bond lower than that of a double bond between the same atoms? (2 marks)

What is resonance? Why is the actual structure of O3 a hybrid? (2 marks)

Why does NaCl have a high melting point? (2 marks)

Why is the dipole moment of CO2 zero though C-O bonds are polar? (2 marks)

What is a coordinate bond? Give an example. (2 marks)

What are the conditions for the combination of atomic orbitals in MOT? (2 marks)

Explain why HF has a higher boiling point than HCl. (2 marks)

Why does PCl5 exist but NCl5 does not? (2 marks)

What is meant by bond enthalpy? (2 marks)

Calculate the bond order of He2+ and predict whether it is stable. (3 marks)

Calculate the formal charge on the nitrogen atom in NH4+. (3 marks)

The dipole moment of HBr is 0.79 D and its bond length is 141 pm. Calculate the percentage ionic character (e = 1.602 x 10^-19 C, 1 D = 3.336 x 10^-30 C m). (3 marks)

Calculate the number of electrons in bonding and antibonding molecular orbitals of N2, and its bond order. (3 marks)

Calculate the total number of sigma and pi bonds in CH2=CH-C(triple bond)CH. (3 marks)

Read the passage and answer the questions. Methane, ammonia and water all have four electron pairs around the central atom. In methane, all four are bond pairs, the shape is tetrahedral and the bond angle is 109.5 degrees. In ammonia, there is one lone pair and the bond angle is 107 degrees. In water there are two lone pairs and the angle is 104.5 degrees. (i) What is the hybridisation of the central atom in each? (ii) Why does the bond angle decrease from methane to water? (iii) What is the shape of H2O? (5 marks)

Read the passage and answer the questions. According to molecular orbital theory, the electrons in a molecule are present in molecular orbitals associated with the nuclei. The number of molecular orbitals formed is equal to the number of combining atomic orbitals. Bonding molecular orbitals have lower energy and greater stability than the corresponding antibonding molecular orbitals. (i) What is the bond order of O2? (ii) Why does O2 show paramagnetism? (iii) Arrange O2, O2+, O2- in order of stability. (5 marks)

Read the passage and answer the questions. The ozone molecule cannot be represented accurately by a single Lewis structure. Experimentally, both O-O bonds in ozone are of equal length (128 pm), intermediate between an O-O single bond (148 pm) and an O=O double bond (121 pm). (i) What is this phenomenon called? (ii) Why are both bonds equal in length? (iii) Draw the canonical structures of O3. (5 marks)

Read the passage and answer the questions. A student noticed that water boils at 373 K, whereas H2S, a heavier molecule, is a gas at room temperature. Similarly, ethanol boils at a much higher temperature than dimethyl ether, though both have the same molecular formula. (i) What type of bonding explains this? (ii) Why does H2S not show it strongly? (iii) Why does ice float on water? (5 marks)

Read the passage and answer the questions. In PCl5, phosphorus uses sp3d hybrid orbitals. Three P-Cl bonds lie in one plane at 120 degrees to each other and are called equatorial bonds. The remaining two bonds lie above and below this plane at 90 degrees and are called axial bonds. (i) What is the shape of PCl5? (ii) Why are axial bonds slightly longer? (iii) Why is PCl5 more reactive than PCl3? (5 marks)

Explain the Kossel-Lewis approach to chemical bonding. Explain the octet rule and its limitations with examples. (6 marks)

Explain the VSEPR theory. Predict the shapes of molecules with 2 to 6 electron pairs with examples. (6 marks)

Explain the valence bond theory and the concept of hybridisation with examples of sp, sp2, sp3, sp3d and sp3d2. (6 marks)

Explain the molecular orbital theory. Draw the energy level diagrams of N2 and O2 and calculate their bond orders. (6 marks)

Explain hydrogen bonding and its types with examples. How does it affect physical properties? (6 marks)