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Which solvent(s) would one use to dissolve each of the following compounds? (Choices: water, a...

Question:

Which solvent(s) would one use to dissolve each of the following compounds? (Choices: water, a polar organic solvent, or a nonpolar organic solvent)

A. {eq}\rm NaI {/eq}.

B. {eq}\rm H_3CCH_2CH_2OH {/eq}.

C. {eq}\rm H_3CCH_2CH_2CH_2CH_2CH_2CH_2CH_3 {/eq}.

Intermolecular Forces of Attraction:

The force responsible for holding the particles of a substance together is called intermolecular force of attraction (IMFA). Examples of IMFAs are electrostatic forces, dipole-dipole forces, hydrogen bonding, and London dispersion forces. The structure of the substance helps determine the dominant IMFA present.

Answer and Explanation: 1

Determining the intermolecular force (IMF) dominant in a substance is essential in knowing whether two substances are soluble in each other. The general rule is substances having relatively similar IMF are soluble in each other.


A. Sodium iodide, {eq}\rm NaI {/eq}, is an ionic compound made up of positively charged sodium ion and negatively charged iodide. This separation of charges demands that the compound is soluble in a solvent that generally has a good separation of charges. This makes water a good solvent to dissolve sodium iodide in. Water is a polar molecule which means that it has a partially positive atom (hydrogen) and a partially negative one (oxygen).


B. Propanol, {eq}\rm H_3CCH_2CH_2OH {/eq}, contains a hydroxyl group, OH, group that is capable of hydrogen bonding which is an IMF formed when a molecule has a hydrogen atom bonded to O, N, or F. Because of this, we can expect it to be soluble in water which also contains an OH group capable of hydrogen bonding. Moreover, we can expect propanol to be soluble in a polar organic solvent. Hydrogen bonding is a special type of dipole-dipole force that exists between polar molecules. Since propanol is a polar molecule, we can expect it to be soluble in another polar solvent. The alkyl group of propanol, {eq}\rm CH_3CH_2CH_2 {/eq}, makes it more compatible with an organic solvent since an organic solvent usually contains an alkyl component as well. Both having alkyl and polar groups make propanol highly soluble in a polar organic solvent.


C. Octane, {eq}\rm H_3CCH_2CH_2CH_2CH_2CH_2CH_2CH_3 {/eq} is made up of C-H and C-C bonds which are nonpolar bonds. Because of this, it is a nonpolar molecule and, thus, has London dispersion force as its primary IMF. We expect it to be soluble with another nonpolar molecule. Thus, octane will be highly soluble in a nonpolar organic solvent.


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Hydrogen Bonding, Dipole-Dipole & Ion-Dipole Forces: Strong Intermolecular Forces

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Chapter 5 / Lesson 13
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Hydrogen bonds are a critical part of many chemical processes, and they help determine the properties of things necessary for life, such as water and protein. Explore hydrogen bonds, as well as dipole-dipole forces, ion-dipole forces, strong intermolecular forces, and intramolecular forces. Understand the effects that intermolecular forces have on certain molecules' properties.


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