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Molecular structures of acetone and water

Question 1: Draw the molecular structures of acetone and water

Solution 1:

Acetone (Chemical Formula: C3H6O)

Acetone is a simple organic compound composed of carbon (C), hydrogen (H), and oxygen (O) atoms.

Drawing Acetone

We represent atoms in molecular structures using symbols (C for carbon, H for hydrogen, and O for oxygen) and lines to indicate chemical bonds between them. Here’s how we draw acetone.

Water (Chemical Formula: H2O)

Water is a simple compound consisting of two hydrogen (H) atoms and one oxygen (O) atom.

Drawing Water

We represent water’s molecular structure like this:

  H
   \
    O
   /
  H

Question 2: Which inter-molecular forces (IMF’s) are utilized by each compound

Solution 2:

Let’s analyze the intermolecular forces (IMFs) utilized by each of the two compounds, acetone (CH3COCH3) and water (H2O):

Acetone (CH3COCH3)

1. Acetone is a covalent compound composed of carbon (C), hydrogen (H), and oxygen (O) atoms.
2. The primary intermolecular forces acting in acetone are:
   • London Dispersion Forces (Van der Waals Forces): These forces are present in all molecules and are due to temporary fluctuations in electron distribution. In acetone, London dispersion forces occur between the molecules due to the motion of electrons around the atoms.
   • Dipole-Dipole Interactions: Acetone has a polar covalent bond between the carbon and oxygen atoms (C=O). This results in a permanent dipole moment, and thus, acetone molecules can experience dipole-dipole interactions with each other.

Water (H2O)

1. Water is also a covalent compound composed of hydrogen (H) and oxygen (O) atoms.
2. The primary intermolecular forces acting in water are:
   • Hydrogen Bonding: Water molecules are strongly attracted to each other through hydrogen bonding. This occurs because the oxygen atom in one water molecule is highly electronegative and can form a hydrogen bond with a hydrogen atom in another water molecule. Hydrogen bonds are stronger than dipole-dipole interactions, which are weaker forces seen in acetone.

Summary

1. Acetone (CH3COCH3) primarily utilizes London Dispersion Forces (Van der Waals Forces) and Dipole-Dipole Interactions as its intermolecular forces.
2. Water (H2O) primarily utilizes Hydrogen Bonding as its intermolecular force, which is significantly stronger than the forces in acetone due to the presence of hydrogen bonds between water molecules.

Question 3: How are these IMF’s depicted? (draw the interaction between molecules)

Solution 3:

let’s depict how the inter molecular forces (IMFs) are represented between molecules for both acetone and water:

Acetone (CH3COCH3)

London Dispersion Forces (Van der Waals Forces)

These forces are relatively weaker and result from temporary fluctuations in electron distribution. They are depicted as temporary dipoles caused by electron movement. In the case of acetone, we can represent this as follows:Imagine two acetone molecules approaching each other. Due to electron movement, a temporary dipole moment is created in one molecule, which induces an opposite temporary dipole in the neighboring molecule. This results in an attractive force between them, as shown below:

δ+          δ-
CH3COCH3 CH3COCH3
δ-          δ+

Dipole-Dipole Interactions

Acetone has a polar covalent bond between the carbon and oxygen atoms (C=O). This results in a permanent dipole moment in each acetone molecule. Dipole-dipole interactions occur when the positive end of one molecule is attracted to the negative end of another. Here’s a simplified representation:

δ+  δ-           δ+  δ-
CH3COCH3       CH3COCH3
δ-  δ+           δ-  δ+

Water (H2O):

Hydrogen Bonding

Hydrogen bonding is a strong IMF and is represented by a dashed or dotted line between the hydrogen atom of one water molecule and the oxygen atom of another water molecule. These bonds are significantly stronger than dipole-dipole interactions. Here’s a depiction:

H  -  O  -  H
 \ /    \ /
  O      O
 / \    / \
H   -  O   -  H

Question 4: Why does water have a higher boiling point than acetone?

Solution 3:

Water has a higher boiling point than acetone primarily due to differences in the strength and nature of their intermolecular forces and the molecular structure of the two compounds.

Intermolecular Forces (IMFs)

Water (H2O):

Water primarily relies on hydrogen bonding as its dominant intermolecular force. Hydrogen bonds are exceptionally strong compared to other IMFs. These bonds form between the hydrogen atom of one water molecule and the oxygen atom of another water molecule.

Hydrogen bonding requires a significant amount of energy to break, which means that water molecules are held together very tightly. This makes it more difficult for water to transition from the liquid to the gaseous state (boil).

Acetone (CH3COCH3):

Acetone mainly utilizes dipole-dipole interactions and London dispersion forces (Van der Waals forces) as its intermolecular forces. While these forces are present in acetone, they are weaker compared to hydrogen bonds.

Dipole-dipole interactions and London dispersion forces are relatively easier to overcome, requiring less energy to break the bonds between acetone molecules. As a result, acetone boils at a lower temperature compared to water.

Molecular Structure

Water (H2O):

Water has a highly polar molecule with two hydrogen atoms and one oxygen atom. The oxygen atom is significantly electronegative, leading to a partial negative charge (δ-) on the oxygen and partial positive charges (δ+) on the hydrogen atoms.

This polarity and the presence of hydrogen atoms result in strong hydrogen bonding between water molecules.

Acetone (CH3COCH3):

Acetone also has a polar molecule due to the presence of the carbonyl group (C=O), which results in a partial positive charge on the carbon atom and a partial negative charge on the oxygen atom.

While acetone exhibits dipole-dipole interactions due to its polarity, it lacks hydrogen bonding sites like those present in water.

Boiling Point Comparison

Considering the above factors:

• Water molecules are held together by strong hydrogen bonds, which require a lot of energy to break. This means that water has a high boiling point of 100 degrees Celsius (212 degrees Fahrenheit) under standard atmospheric pressure.
• Acetone molecules have weaker intermolecular forces, primarily dipole-dipole interactions and London dispersion forces, which are easier to overcome. As a result, acetone has a lower boiling point of 56.2 degrees Celsius (132.2 degrees Fahrenheit) under standard atmospheric pressure.

Summary:

Water has a higher boiling point than acetone because it exhibits strong hydrogen bonding, which requires more energy to break compared to the weaker intermolecular forces present in acetone. Additionally, the molecular structure of water, with its highly polar nature and hydrogen bonding sites, contributes to its higher boiling point.

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