Determining When Molecular Compounds Ionize When Dissolved Into Water

In summary, the individual properties of molecular compounds, such as electronegativity and electron distribution, determine their ability to ionize and yield hydrogen ions when dissolved in water. In the case of ethanol, the pKs value and the equilibrium of the dissociation reaction largely keep the compound in its molecular form. However, under certain conditions, the -OH bond can dissociate and result in the formation of a base. On the other hand, molecules like methane and sucrose do not have the necessary properties to easily ionize and yield hydrogen ions.
  • #1
Mazurka
10
0
Hello,

This is a matter I have been having some difficulties with for the past few days. My question: How is it that I would go about distinguishing molecular compounds in regards to their capacity to ionize and yield hydrogen ions when dissolved into distilled water?

For example, if ethanol (C2H5OH) was dissolved into water, why couldn't the hydrogen atom in the compound ionize and result in the formation of an acid? Couldn't the -OH bond dissociate and result in the formation of a base? Similarly, why is it that methane (CH4) or sucrose (C12H22O11) cannot ionize and yield hydrogen ions?

This may be common knowledge and I may have been merely mislead. However, I am enrolled in a high school program and I understand that at this level, a lot of details in the sciences are simply left out. I greatly appreciate any clarity or enlightenment anyone can offer me.

Thank you,

Eric.
 
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  • #2
Mazurka said:
For example, if ethanol (C2H5OH) was dissolved into water, why couldn't the hydrogen atom in the compound ionize and result in the formation of an acid?

It can, but the pKs is 15,90. Thant means the equilibrium C2H5OH + H2O <=> C2H5O- + H3O+ is almost on the left side.

Mazurka said:
Couldn't the -OH bond dissociate and result in the formation of a base?

It can, e.g. C2H5OH + Na -> C2H5ONa + ½ H2

Mazurka said:
Similarly, why is it that methane (CH4) or sucrose (C12H22O11) cannot ionize and yield hydrogen ions?

C in CH4 is not as interested in the electrons of hydrogen as for example Cl in HCl. In simple molecules acidity is mainly caused by the electronegativity. In complex molecules (e.g. with delocalized electrons) there might be other mechanisms too.
 

1. How do you determine if a molecular compound will ionize when dissolved in water?

Determining if a molecular compound will ionize when dissolved in water depends on the compound's ability to form ions in solution. Generally, compounds that contain polar covalent bonds and are composed of highly electronegative atoms are more likely to ionize in water.

2. What factors affect the ionization of molecular compounds in water?

The strength of the bond between the atoms in a molecular compound and the polarity of the compound are the two main factors that affect its ionization in water. As the bond strength decreases and the polarity increases, the likelihood of ionization also increases.

3. How does the concentration of a molecular compound in water affect its ionization?

The concentration of a molecular compound in water does not directly affect its ionization. However, a higher concentration of the compound can result in a higher concentration of ions in solution due to the increased number of molecules that can potentially ionize.

4. Can all molecular compounds ionize in water?

No, not all molecular compounds can ionize in water. Only compounds with polar covalent bonds and those composed of highly electronegative atoms have the potential to ionize in water. Non-polar compounds or those with weaker bonds are less likely to ionize in water.

5. How can you experimentally determine if a molecular compound will ionize in water?

One way to experimentally determine if a molecular compound will ionize in water is by conducting a conductivity test. If the solution is able to conduct electricity, it is an indication that ions are present and the compound has ionized in water. Another method is by observing the change in pH of the solution, as the presence of ions can alter the pH of the solution.

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