14. Bonding

Which statements correctly describe the NO2- ion? I. It can be represented by resonance structures. II. It has two lone pairs of electrons on the N atom. III. The N atom is sp2 hybridized. A. I and II only B. I and III only C. II and III only D. I, II and III

10 B

Which is the smallest bond angle in the PF5 molecule? A. 90 B. 109.5 C. 120 D. 180

11 A

Which molecule is square planar in shape? A. XeO4 B. XeF4 C. SF4 D. SiF4

14 B

How many sigma (σ) and pi (π) bonds are present in the structure of HCN? σ π A. 1 3 B. 2 3 C. 2 2 D. 3 1

18 C

What is the number of sigma () and pi () bonds and the hybridization of the carbon atom in Sigma Pi Hybridization A. 4 1 sp2 B. 4 1 sp3 C. 3 2 sp3 D. 3 1 sp2

2 A

Explain the meaning of the term hybridization.

20a mixing/joining together/combining/merging of atomic orbitals to form molecular orbitals/new orbitals/orbitals of equal energy;

State the type of hybridization shown by the carbon atom in the H-C≡N molecule, and the number of and bonds present in the C≡N bond

20b sp; Do not award mark if sp2 or sp3 is also stated. one sigma and two pi (bonds);

Describe how sigma and pi bonds form.

20c (sigma bond formed by) end-on/axial overlap; electrons/electron density between the two (carbon) atoms/OWTTE; (π bond formed by) sideways/parallel overlap; electrons/electron density above and below bond/OWTTE; 4 Marks can be scored from a suitable diagram. Do not award 2nd and 4th marks if electrons are not mentioned.

Atomic orbitals can mix by hybridization to form new orbitals for bonding. Identify the type of hybridization present in each of the three following molecules. Deduce and explain their shapes. (i) OF2

23a OF2 sp3; V-shaped/bent/angular; 2 bonding + 2 non-bonding (electron pairs); 3

PCl3, PCl5, POCl3 Draw a Lewis structure for each molecule in the gas phase. (Show all non-bonding electron pairs.), which one is polar, explain

24(i) Award [1] for each correct Lewis structure. 3 Accept use of dots or crosses to represent electron pairs. Subtract [1] if non-bonding pair on P in PCl3 is missing. Subtract [1] if non-bonding pair(s) on Cl or O are missing. Accept legitimate alternatives for POCl3, e.g. see below. 24 (iii) PCl3 polar, polarities do not cancel/OWTTE; PCl5 non-polar, polarities cancel/OWTTE; POCl3 polar, polarities do not cancel/OWTTE; Award [2] for three polarities correct, [1] for two polarities correct, and [1] for correct reason(s). Accept argument based on dipole moments. Allow ECF if based on legitimate chemical structure.

State the meaning of the term hybridization. State the type of hybridization shown by the nitrogen atoms in N2, N2H2 and N2H4.

27(a) hybridization: mixing/merging of atomic orbitals; N2 −sp; N2H2 −sp2;N2H4 −sp3;

Which of the following contain a bond angle of 90°? I. PC14+ II. PCl5 III. PCl6- A. I and II only B. I and III only C. II and III only D. I, II and III

3 C

Using the Data Booklet, predict and explain which of the bonds O-H, O-N or N-H would be most polar.

31v O-H is most polar; O-H has greatest difference between electronegativities/calculation showing values of 1.4, 0.5 and 0.9 respectively;

Which allotropes contain carbon atoms with sp2 hybridization? I. Diamond II. Graphite III. C60 fullerene A. I and II only B. I and III only C. II and III only D. I, II and III

4 C

Which statement about sigma and pi bonds is correct? A. Sigma bonds are formed only by s orbitals and pi bonds are formed only by p orbitals. B. Sigma bonds are formed only by p orbitals and pi bonds are formed only by s orbitals. C. Sigma bonds are formed by either s or p orbitals, pi bonds are formed only by p orbitals. D. Sigma and pi bonds are formed by either s or p orbitals.

6 C

Consider the following statements. I. All carbon-oxygen bond lengths are equal in CO32-. II. All carbon-oxygen bond lengths are equal in CH3COOH. III. All carbon-oxygen bond lengths are equal in CH3COO-. Which statements are correct? A. I and II only B. I and III only C. II and III only D. I, II and III

7 B

Which statement is correct about multiple bonding between carbon atoms? A. Double bonds are formed by two π bonds. B. Double bonds are weaker than single bonds. C. π bonds are formed by overlap between s orbitals. D. π bonds are weaker than sigma bonds.

8 D