Questions and Answers
Which molecule has a higher dipole moment?
Why does NF3 have a lower dipole moment than NH3?
What defines a coordinate covalent bond?
In a coordinate covalent bond, what is the role of the donating atom?
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Which of the following molecules involves a coordinate covalent bond in its formation?
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How is a coordinate covalent bond represented in diagrams?
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What happens to the stability of atoms after the formation of a coordinate covalent bond?
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What is another name for a coordinate covalent bond?
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What is the primary requirement for hydrogen bonding to occur?
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How do hydrogen bonds compare to covalent bonds?
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In the context of water molecules, what charge does the oxygen atom develop?
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What type of intermolecular forces does hydrogen bonding fall under?
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Which of these statements best describes hydrogen bonding?
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What occurs to a molecule when hydrogen bonds are formed?
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Which statement is true regarding the characteristics of hydrogen bonds?
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Which elements are known to form hydrogen bonds when bonded with hydrogen?
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What is required for hydrogen bonding to occur?
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Which of the following compounds can form hydrogen bonds?
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What is the nature of hydrogen bonds compared to van der Waals forces and covalent bonds?
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How does hydrogen bonding affect the boiling point of compounds?
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What causes the lower density of ice compared to liquid water?
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Which property is affected by hydrogen bonding resulting in higher surface tension?
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What characteristic of lower alcohols allows them to be soluble in water?
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Which factor increases the strength of a hydrogen bond?
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What is the reason ice floats on water?
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Which type of hydrogen bonding occurs between different molecules?
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What characterizes intramolecular hydrogen bonding?
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What is the bond angle in the water molecule?
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How does the electronegativity of atoms influence hydrogen bonding?
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What is the role of non-bonding electron pairs in water's molecular structure?
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In which of the following compounds is hydrogen bonding significant?
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What determines the arrangement of electron pairs around the oxygen in water?
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What primarily causes the concentration of negative charge at the oxygen end of a water molecule?
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What is the nature of the attraction between the negative end of one water molecule and the positive end of another?
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How do hydrogen bonds in water compare in strength to O--H covalent bonds?
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What happens to hydrogen bonds when water is in a gas phase?
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How many neighboring molecules does an H2O molecule typically bind to in liquid water due to thermal motions?
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What configuration do H2O molecules ideally settle into when water freezes into ice?
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What effect does the small mass of water have on its ability to form hydrogen bonds?
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What happens to the hydrogen bonds in water when thermal motion is reduced, such as when cooling occurs?
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Study Notes
Dipole Moment Comparison
- NH₃ (ammonia) has a higher dipole moment (1.24 D) than NF₃ (nitrogen trifluoride) which has a dipole moment of 0.24 D.
- In NF₃, fluorine is more electronegative than nitrogen, leading to an unequal electron pull that reduces the overall dipole moment.
- NH₃'s hydrogen atoms do not have sufficient electronegativity to overcome the nitrogen's pull, resulting in a stronger dipole moment compared to NF₃.
Coordinate Covalent Bond
- A coordinate bond is formed when one atom donates both electrons for a shared pair, also known as a dative or dipolar bond.
- The atom that donates the electron pair is referred to as the donor, while the atom that accepts these electrons is called the acceptor.
- This bond is represented with an arrow pointing from the donor to the acceptor.
- After electron sharing, both atoms achieve stability, a concept central to Lewis theory.
Formation of Ammonium Ion
- In forming the ammonium ion (NH₄⁺), the nitrogen atom in ammonia donates its electron pair to the empty orbital of an H⁺ ion, establishing a coordinate bond.
Hydrogen Bonding
- Hydrogen bonding is a dipole-dipole interaction between hydrogen atoms covalently bonded to a highly electronegative atom and another electronegative atom nearby.
- Example: In water (H₂O), the oxygen atom is more electronegative than hydrogen, leading to partial negative (δ-) and partial positive (δ+) charges, facilitating hydrogen bonding.
- Hydrogen bonds are weaker than covalent or ionic bonds but stronger than normal dipole-dipole and van der Waals forces.
Conditions for Hydrogen Bonding
- A highly electronegative atom must be linked to a hydrogen atom, leading to polarization of the molecule.
- The electronegative atom should ideally be small, enhancing electrostatic attraction and hydrogen bonding potential.
Properties of Hydrogen Bonding
- Solubility: Lower alcohols can dissolve in water due to hydrogen bonding with water molecules.
- Volatility: Compounds with hydrogen bonds have higher boiling points and thus lower volatility.
- Viscosity and Surface Tension: Substances with hydrogen bonds exhibit higher viscosity and surface tension due to their associated molecular structure.
- Density of Ice: Ice is less dense than water because hydrogen bonding creates a cage-like structure in solid ice, allowing molecules to be less packed than in liquid water.
Types of Hydrogen Bonding
- Intermolecular Hydrogen Bonding: Occurs between different molecules, as seen in water and ammonia.
- Intramolecular Hydrogen Bonding: Takes place within a single molecule where one hydrogen atom is linked to an electronegative atom and forms a bond with another electronegative atom within the same molecule.
Unique Properties of Water
- Water's arrangement due to hydrogen bonding leads to a distorted tetrahedral shape, giving it unique properties such as a high heat capacity and surface tension.
- As water freezes, a stable network of hydrogen bonds forms, making ice less dense than liquid water and allowing ice to float.
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Description
This quiz explores the comparison of dipole moments between ammonia (NH3) and nitrogen trifluoride (NF3). It delves into the electronegativity effects of the constituent atoms and how they influence the overall dipole moment of each molecule. Test your understanding of molecular polarity and electronegativity with this focused quiz!
