Chemical Bonding and Structure
Competition questions
25 marksThe melting point of CaS is higher than that of KCl. Which of the following are explanations for the observation?
I Ca2+ is more positively charged than K+.
II S2− is more negatively charged than Cl−.
III The K+ ion is smaller than the Ca2+ ion.
2023 SJChO P1 Q36
Which statement about metals is not correct?
2024 USS O Prelim P2 Q8
Two statements about the structure and properties of metals are given.
statement 1: Metals are malleable and have high melting points.
statement 2: Metals have mobile electrons in their structure.
Which statement is correct?
2024 Woodlands O Prelim P1 Q9
The table shows the sixth ionisation energies of four consecutive elements in the Periodic Table.
| element | W | X | Y | Z |
|---|---|---|---|---|
| sixth ionisation energy / kJ mol−1 | 19 800 | 21 300 | 8500 | 9360 |
What is the formula of the fluoride of W?
Source: 2024 VJC J2 Prelim P1 Q2
Diazene has the molecular formula N2H2. Given that nitrogen and hydrogen show their usual numbers of bonds, which describes the shape and bond angle around each central atom? Each option gives the shape, then the bond angle.
2019 CJC J2 Prelim P1 Q4
Iodine and phosphorus each form a trifluoride. What are the shapes of these two molecules? Each option gives IF3, then PF3.
2020 ACJC J1 Promo Q6
The valence shell electron pair repulsion (VSEPR) theory is used to predict the bond angles of molecules. Which bond angle is correctly predicted by VSEPR?
| bond pairs around the central atom | lone pairs around the central atom | bond angle | |
|---|---|---|---|
| A | 2 | 1 | 105° |
| B | 2 | 2 | 118° |
| C | 3 | 1 | 107° |
| D | 3 | 2 | 90° |
2024 HCI J2 Prelim P1 Q3
Which one of the following pairs of compounds shows the same shape and similar bond angles?
2022 VJC J1 Promo P1 Q4
In which pair of molecules or ions do both species contain a bond angle of 107°?
SJChO Mock 3 P1 Q29
When an iodine atom is covalently bonded to an electron-withdrawing group X, the electron density on the large iodine atom becomes uneven. The tip of the iodine atom directly opposite the X–I bond becomes very electron-deficient, while the region round the middle of the iodine atom is electron-rich. The electron-deficient region can attract an anion A− without forming a covalent bond. What is the most likely X–I···A− bond angle for this attraction? (··· shows the non-covalent attraction.)
2023 SJChO P1 Q6
The table identifies the shape and polarity of four molecules. Which row is correct?
| molecule | molecular shape | polarity | |
|---|---|---|---|
| A | xenon tetrafluoride | tetrahedral | non-polar |
| B | selenium hexafluoride | T-shaped | non-polar |
| C | trichloromethane | tetrahedral | polar |
| D | boron trichloride | trigonal planar | polar |
2024 ASRJC J2 Prelim P1 Q4
The table shows the boiling points of some halogenoalkanes.
| compound | boiling point / °C |
|---|---|
| CH3CH2Cl | 12.3 |
| CH3CH2Br | 34.8 |
| CH3CH2I | 70.0 |
Which of the following correctly explains the difference in the boiling points?
1 The electronegativity difference between the halogen and carbon increases from C–Cl to C–I.
2 The strength of permanent dipole–permanent dipole attraction increases from C–Cl to C–I.
3 The strength of instantaneous dipole–induced dipole attraction increases from CH3CH2Cl to CH3CH2I.
4 The bond energy of the carbon–halogen bond decreases from C–Cl to C–I.
2019 YIJC J1 MYE P1 Q13
Which of the following substances consists of atoms or molecules held together only by instantaneous dipole–induced dipole forces of attraction?
2019 YIJC J1 MYE P1 Q14
Information about some hydrocarbons is given below.
| hydrocarbon | boiling point / °C |
|---|---|
| ethane, CH3CH3 | –89.0 |
| propane, CH3CH2CH3 | –42.0 |
| butane, CH3CH2CH2CH3 | –1.7 |
| 2-methylpropane, (CH3)3CH | –11.7 |
Which statements help to explain the variation in boiling points of the hydrocarbons?
1 Presence of more hydrogen atoms results in stronger hydrogen bonding.
2 Presence of more covalent bonds results in more energy required to break them.
3 Greater surface area of contact results in stronger instantaneous dipole–induced dipole interactions.
4 Presence of more electrons results in stronger instantaneous dipole–induced dipole interactions.
2020 VJC J1 Promo P1-P2 Q5
Information about the properties of some compounds is given below.
| compound | boiling point / °C |
|---|---|
| HF | 19.5 |
| NH3 | −33.3 |
| H2O | 100 |
Which statement about the hydrogen bonding in these compounds is correct?
2022 MI J2 Prelim P1 Q7
The boiling point of water (100 °C) is greater than that of HF (20 °C). Which statement is a correct explanation of this?
2023 NJC J2 Prelim P1 Q3
The boiling points of H2O, H2S and H2Se are different. Which statements are correct?
I H2S has a lower boiling point than H2Se because H2S molecules have weaker permanent dipole–permanent dipole forces of attraction.
II H2O molecules experience weaker temporary dipole–induced dipole forces of attraction than H2Se molecules.
III H2O molecules experience stronger permanent dipole–permanent dipole forces of attraction than H2S molecules.
SJChO Mock 3 P1 Q17
Use the table of densities and boiling points of five solvents.
| solvent | molecular formula | density / g cm−3 | boiling point / °C | |
|---|---|---|---|---|
| I | chloroform | CHCl3 | 1.49 | 61 |
| II | ethanol | C2H5OH | 0.79 | 78 |
| III | acetone | (CH3)2CO | 0.78 | 56 |
| IV | hexane | C6H14 | 0.66 | 69 |
| V | water | H2O | 1.00 | 100 |
Which pair of liquids can be separated by liquid–liquid extraction?
Source: 2023 SJChO P1 Q28
Which lattice structure is correctly described?
| lattice structure | description | |
|---|---|---|
| A | giant molecular | lattice of molecules held together by strong covalent bonds |
| B | giant ionic | each cation is only bonded to the anion to which electrons are transferred |
| C | giant metallic | all electrons are delocalised within the metal cation lattice |
| D | simple molecular | molecules held together by weak intermolecular forces |
2021 DHS J2 Prelim P1 Q4
Silicon carbide is a shiny, hard and chemically inert material with a very high melting point. It can be used to sharpen knives and make crucibles. Which type of structure explains these properties?
2021 RVHS J1 Common Test P1 Q9
Substances X, Y and Z are all solids. Some of their physical properties are given in the table.
| substance | X | Y | Z |
|---|---|---|---|
| melting point / °C | 772 | 114 | 1610 |
| boiling point / °C | 1407 | 183 | 2205 |
| electrical conductivity when molten | good | poor | poor |
What type of structure could each substance have? Each option gives X, Y and Z in that order.
2021 YIJC J1 MYE P1 Q10
Which row correctly describes the structure and bonding present in the solid lattice of the given substance?
| substance | structure | bonding | |
|---|---|---|---|
| A | ice | giant molecular | covalent and hydrogen bonding |
| B | iodine | simple molecular | covalent bonding and permanent dipoles |
| C | sodium sulfate | giant ionic | ionic and covalent bonding |
| D | copper | giant metallic | ionic bonding |
2023 DHS J2 Prelim P1 Q4
Which property of X2 increases down the group for X = Cl, Br or I?
2024 RI J2 Prelim P1 Q11
Which statement about covalent bonds is true?
2022 EJC J1 MYE P1 Q3, adapted
Consider these chlorine-containing species: ICl2−, ClF3, ClO3−. Which statements about them are correct?
1 The bond angles increase in the order ClF3, ClO3−, ICl2−.
2 Two of the three species have an overall dipole moment.
3 Only ClO3− is not planar.
2020 VJC J1 Promo P1-P2 Q4
