RI Chemical Bonding I Remedial

Name: ………………………………………. ( ) Class: ……………. Date: ……………. Raffles Institution Year 5 H2 Chemistry 2024 ChemFocus T3W5 – Chemical Bonding 1 Notes:  Pre-ChemFocus Activity  • Rewatch lecture video on how to draw dot-and-cross for molecules IVY > C2025 – H2 CHEMISTRY (FOR LECTURES) > 4.3 (Dot-&-cross Diagrams of Simple Covalent Molecules) • Watch the online Info-pack video IVY > C2025 – H2 CHEMISTRY > Pages > [ChemFocus] T3W5 Chemical Bonding > First video ONLY

Self-Check Questions 1. Complete the following table. Substances Structure Bonding affecting melting/boiling point ICl MnSO4 BH3 NaBrO3 CH3OH 2. Complete the following table. molecule dot-and-cross diagram shape of molecule structure (include lone pair of e– on central atom) Check the boxes with (✓/⨉) to check for polarity Predominant intermolecular interactions NH3 trigonal pyramidal H N H H ☑ polar bond present ☑ net dipole moment polar / non-polar ☑ polar molecule ☑ H bonded to FON ☑ lp of e– on FON id-id / pd-pd / H-bond CO2 ☐ polar bond present ☐ net dipole moment polar / non-polar ☐ polar molecule ☐ H bonded to FON ☐ lp of e– on FON id-id / pd-pd / H-bond H2O ☐ polar bond present ☐ net dipole moment polar / non-polar ☐ polar molecule ☐ H bonded to FON ☐ lp of e– on FON id-id / pd-pd / H-bond SO2 ☐ polar bond present ☐ net dipole moment polar / non-polar ☐ polar molecule ☐ H bonded to FON ☐ lp of e– on FON id-id / pd-pd / H-bond Learning point(s): Check your answers at IVY > C2025 – H2 CHEMISTRY > Pages > [ChemFocus] T3WX Chemical Bonding > Remaining videos

3. Draw a dot-and-cross diagram to illustrate the electron arrangement in the following substances. 1. CO32– 2. ICl2+ Learning point(s): Learning point(s): 4. In terms of structure and bonding, explain why the melting point of MgO is higher than that of SO 2. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. Learning point(s): 5. In terms of structure and bonding, explain why the boiling point of carbon dioxide is lower than that of ethanol. CC O ethanol C O O carbon dioxide H H H H H H ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. Learning point(s):

Tutorial Discussion Questions (to complete before Chemfocus session) 1a Draw a dot -and-cross diagram to illustrate the electron arrangement in the following substances. [3] (1) O3 Learning point(s): (2) ClO2+ Learning point(s): (3) NO3– Learning point(s): 2a The structures of the molecules, including the lone pair of electrons on the central atoms, are provided in the table below. Complete the table by indicating the shape, polarity and interactions between the molecules. Structure of molecule shape and bond angle Is it polar? (✓/ ⨉) Predominant IMFOA (id-id/pd-pd/H-bond) e.g. S HH bent, 105 ° ✓ Permanent dipole- permanent dipole P H H H B HH H C H F H H H Cl O

3a (i) The melting point of NaCl was found to be 801 °C. Suggest, with reasons, whether the melting point of MgO will be higher or lower than that of NaCl. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] Learning point(s): (ii) In terms of structure and bonding, explain why SiCl4 has a lower boiling point than H2O. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] Learning point(s): (iii) Draw a labelled diagram to show the significant force of attraction between two water molecules. Include the name of the attraction in your diagram. [2] Learning point(s):

Tutorial In-Class Practice Questions (to be attempted IN CLASS) 1b Draw a dot-and-cross diagram to illustrate the electron arrangement in the following substances. [2] (1) NO2 Learning point(s): (2) ICl4– Learning point(s): 2b The structures of the molecules are provided in the table below. Complete the table by indicating the shape, polarity and interactions between the molecules. (Hint: you should first determine the number of electron density regions and number of lone pair of electrons on the central atom) molecule shape and bond angle Is it polar? (✓/ ⨉) Predominant IMFOA (id-id/pd-pd/H-bond) P ClCl Cl ClCl S C O P OHHO OH (about P) Si F F F F H C H H O H (about C)

3b (i) Use of the Data Booklet is relevant to this question. The following table shows the theoretical and experimental lattice energies of CaSO4 and MnSO4. compound theoretical lattice energy / kJ mol−1 experimental lattice energy / kJ mol−1 CaSO4 −2480 −2489 MnSO4 −2825 −2920 Explain why the theoretical and experimental values of lattice energy differ more for MnSO4 as compared to CaSO4. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] Learning point(s): (ii) Explain why the melting point of H2O (0 °C) is lower than that of I2 (387 °C). ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] Learning point(s):

(iii) Iron(II) chloride is an ionic compound that dissolves readily in water. With the aid of a suitable diagram, explain why. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[3] Learning point(s):

Self-Check Questions 1. Complete the following table. Substances Structure Bonding affecting melting/boiling point ICl simple molecular structure intermolecular forces of attraction MnSO4 giant ionic lattice structure ionic bonds BH3 simple molecular structure intermolecular forces of attraction NaBrO3 giant ionic lattice structure ionic bonds CH3OH simple molecular structure intermolecular forces of attraction 2. Complete the following table. molecule dot-and-cross diagram shape of molecule structure (include lone pair of e– on central atom) Check the boxes with (✓/⨉) to check for polarity Predominant intermolecular interactions NH3 trigonal pyramidal ☑ polar bond present ☑ net dipole moment polar / non-polar ☑ polar molecule ☑ H bonded to FON ☑ lp of e– on FON id-id / pd-pd / H-bond CO2 linear ☑ polar bond present ☒ net dipole moment polar / non-polar ☒ polar molecule ☒ H bonded to FON ☒ lp of e– on FON id-id / pd-pd / H-bond H2O bent ☑ polar bond present ☑ net dipole moment polar / non-polar ☑ polar molecule ☑ H bonded to FON ☑ lp of e– on FON id-id / pd-pd / H-bond SO2 bent ☑ polar bond present ☑ net dipole moment polar / non-polar ☑ polar molecule ☒ H bonded to FON ☑ lp of e– on FON id-id / pd-pd / H-bond

3. (1) CO32– (2) ICl2+ 4. MgO has a giant ionic lattice structure, while SO2 has a simple molecular structure. More energy is needed to overcome stronger electrostatic forces of attraction between oppositely charged ions in MgO than the weaker intermolecular forces of attraction in SO2. 5. Both CO2 and C2H5OH have simple molecular structure. CO2 is non-polar while C2H5OH is polar. More energy is required to overcome stronger intermolecular hydrogen bond in