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TitleAcid Base Properties
Tags Acid Sodium Hydroxide Properties Of Water Solubility
File Size101.2 KB
Total Pages5
Document Text Contents
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cations. [4] In general, acids and bases react with each other completely yielding salt and water

and this process is called neutralization.

However, some acids and bases are weak that they cannot completely ionize in aqueous

solutions. One way to determine an organic compound’s behavior is to compare its solubility in

aqueous acids and bases. Solubility is the ability of a solvent to dissolve a solute in a solution. It

also refers to the maximum amount of solute that dissolves in a solvent at equilibrium. Solubility

is slightly different from miscibility, which refers to how easily a liquid dissolves in another liquid

when mixed together. Solubility is influenced by the following factors: Temperature, Pressure,

and Polarity. First, high temperature is relevant in increasing the solubility of solid substances.

The principle behind this is that the heat provides the energy to break the bonds in the

molecules of the solid. Second, “the solubility of a gas in a liquid is directly proportional to the

pressure of that gas above the surface of that solution,” (Ophardt, 2003) as stated in Henry’s

Law [5]. As more pressure is applied to the gas molecules, the more it will dissolve in the

solution below it. Nevertheless, changes in pressure do not affect the solubility of liquids and

solids. Third, polarity denotes that like dissolves like. Polar solvents like water dissolve polar

solutes while nonpolar solvents such as hexane dissolve nonpolar solutes.

Results and Discussion

The reagents used in the experiment are hydrochloric acid (HCl), sodium hydroxide

(NaOH), and sodium bicarbonate (NaHCO3). Hydrochloric acid completely dissociates in water,

therefore it is a strong acid. Sodium hydroxide, a strong metallic base, reacts with strong acids

to form water and salts. Sodium bicarbonate, a white crystalline solid, decomposes to water and

carbon dioxide when mixed with acids. Effervescence is a characteristic of decomposition giving

off bubbles in the solution.

As seen in Table 1 on the next page, cyclohexane is an alkane having no functional

group. It is also a neutral compound and cannot form hydrogen bonds because of its nonpolar

characteristic rendering it immiscible in both HCl and NaOH.

Unlike cyclohexane, ethanol can form hydrogen bonds and is considered neutral but can

act as either acid or base. When acting as an acid with pKa of 16, it reacts with NaOH and

exists in equilibrium with the products as illustrated in the equation. [6]

CH3CH2OH + NaOH CH3CH2ONa + H2O

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When acting as a base, it reacts with hydrogen halides such as HCl to yield ethyl halides. This

process of halogenation occurs via a substitution reaction. [6]

CH3CH2OH + HCl → CH3CH2Cl + H2O

Furthermore, the structure of ethanol (with C–H bonds and C–OH bonds) denotes that it

dissolves in both polar and nonpolar substances rendering it miscible in NaOH and HCl.

Amyl acetate, an ester, participates in hydrogen bonding by accepting but not donating

hydrogen bonds. Because of the hydrogen bonding, amyl acetate is more soluble in water than

hydrocarbons but not as polar as alcohols or acids due to its limited bonding. Moreover, esters

cannot form hydrogen bonds with each other [7]. Because of this property of amyl acetate, it is

immiscible in both HCl and NaOH.

With the functional group amine, ethylamine acts as a base almost always. As

mentioned earlier, Lewis bases donate electron pairs. Thus, basicity of amines depends on the

availability of lone electron pairs in the nitrogen atom and on the electronic properties of the

compound’s substituents. Since the N atom in the amine group attaches 2 hydrogen atoms and

an ethyl group, it is considered as a primary amine (R–NH2). Also, the lone pair on the N atom

creates a greater electron density making the amine molecule more basic. [8]

Despite the strong basicity of ethylamine, it still has a slight degree of acidity. This is due

to the fact that its primary amine group has 2 protic hydrogen atoms unlike tertiary amine (R–N–

R), which has no acidic hydrogen. It is also important to note that ethylamine is still more basic

than acidic. [8] It can also form hydrogen bonds just like ethanol and amyl acetate. Thus, being

basic and slightly acidic, it is miscible in both HCl and NaOH. The balanced equations for these

reactions are:

CH3CH2NH2 + HCl → CH3CH2NH3 + Cl (reaction with HCl)

and CH3CH2NH2 + NaOH → CH3CH2NH + H2O + Na (reaction with NaOH).

Phenol or carbolic acid, an aromatic compound, can form hydrogen bonds due to the

alcohol group attached to it. It is only slightly acidic because it has a low tendency of losing its

hydrogen ion and because it is connected to a hydrocarbon exhibiting resonance. When the

hydrogen ion leaves, the delocalized electrons in the resonance make the conjugate base

stable and therefore, make phenol a weak acid. [9] Nonetheless, compared to most alcohols, it

has a higher tendency of donating the hydrogen ion in its alcohol group. Thus, it reacts with

NaOH, a strong base, through the neutralization process.

http://en.wikipedia.org/wiki/Hydrogen_chloride
http://en.wikipedia.org/wiki/Hydrogen_chloride

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