12 Questions
What type of bond is formed when the electronegativity difference is between 0.4 and 1.9?
Polar covalent
What property characterizes polar covalent bonds?
Unequal sharing of electrons
What theory/model is used to predict the geometry of molecules based on electrostatic repulsion?
VSEPR theory
In the molecule BeCl2, what is the shape of the molecule?
Linear
Which molecule has a trigonal pyramidal molecular structure?
NH3
Why are some materials soluble in water but not in kerosene or vice versa?
Due to the polarity of the material and the solvent
Which type of compound has a low melting point due to weak intermolecular forces?
Nonpolar covalent
Why can kerosene not dissolve salt and vetsin?
Kerosene is nonpolar and cannot interact with ionic compounds
Which substance conducts electricity due to the presence of free ions?
Salt solution
Which type of compound is soluble in a polar solvent?
Ionic
What property allows a liquid to resist an external force on its surface?
Surface tension
In which type of interaction do polar molecules containing hydrogen participate?
Hydrogen bond
Study Notes
Electronegativity Difference
- If ∆EN is ≤ 0.4, the bond is nonpolar covalent
- If ∆EN is > 0.4 but < 1.9, the bond is polar covalent
- Ionic compounds are highly polar
Polarity
- Polar covalent bonds: electrons are shared unequally, creating a dipole moment
- Nonpolar covalent bonds: electrons are shared equally
- Ionic bonds: complete transfer of one or more valence electrons, resulting in full charges
Molecular Geometry
- VSEPR (Valence Shell Electron Pair Repulsion) model predicts the geometry of molecules based on electrostatic repulsion
- Each group of valence electrons around the central atom must be located as far from other groups as possible
- Electron Group: a number of electrons that occupy a specific region (lone pair, single bond, double bond, triple bond)
Molecular Geometry Examples
- BeCI2: linear shape
- BCI3: trigonal planar shape
- SO2: bent/angular shape
- NH3: trigonal pyramidal shape
Solubility
- Sugar is polar, wax is non-polar covalent
- Polar solute is soluble in polar solvent, and vice versa (like dissolves like)
- Covalent compounds can be polar or non-polar
Properties of Substances
- Non-polar covalent compounds: low melting point, weak intermolecular forces
- Ionic compounds: high melting point, made up of ions
- Ionic compounds can conduct electricity if ions are free to move
- Sugar solution does not conduct electricity
Chemical Properties
- Solubility: the ability of a substance to dissolve in a solvent
- Melting point: the temperature at which a substance changes from solid to liquid at atmospheric pressure
- Conductivity: the measure of a material's ability to conduct electricity
Intermolecular Forces (IMFA)
- Types of IMFA:
- Ion-dipole: between ionic compounds and polar covalent compounds
- Hydrogen bond: between polar molecules containing hydrogen
- Dipole-dipole: between polar covalent compounds and another polar covalent substance
- Dipole-induced dipole: between polar and nonpolar molecules
Physical Properties
- Vapor pressure: the equilibrium pressure of a vapor above a liquid
- Volatility: how easily a substance will evaporate
- Boiling point: the temperature at which vapor pressure is equal to the pressure of the gas above a liquid
- Viscosity: resistance to flow of a given liquid
- Surface tension: the property of a liquid surface that allows it to resist an external force
Test your knowledge on chemical bonding by identifying whether a bond is nonpolar covalent, polar covalent, or ionic based on electronegativity differences. Also, assess your understanding of molecular geometry for polyatomic molecules.
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