for each of the following compounds, draw the form in which it will predominate at ph=3, ph=6, ph=10, and ph=14.
a)CH3COOH b)CH3CH2NH3 c) CF3CH2OH
please explain how to get answers. my book does not give clear examples.
To determine the form in which each compound will predominate at different pH values, you need to understand the concept of acidic and basic properties. In general, compounds can be classified as acids or bases based on their ability to donate or accept protons (H+ ions).
Here's how you can approach each compound:
a) CH3COOH (Acetic acid):
- CH3COOH is a weak acid that can donate a proton (H+).
- At low pH (pH=3), the acetic acid will largely exist in its protonated form, CH3COOH. This is because the higher concentration of H+ ions in an acidic environment allows the compound to stay in its protonated state.
- At neutral pH (pH=6), acetic acid is still a weak acid, but the concentration of H+ ions decreases. Therefore, the equilibrium between the protonated (CH3COOH) and deprotonated (CH3COO-) forms shifts slightly toward the deprotonated form, although the protonated form is still predominant.
- At higher pH values such as pH=10 and pH=14, the concentration of H+ ions decreases even further. At these alkaline conditions, the equilibrium shifts significantly towards the deprotonated form (CH3COO-), as the basic environment favors the donation of a proton to form more water molecules.
b) CH3CH2NH3 (Ethylamine):
- CH3CH2NH3 is a weak base capable of accepting a proton (H+).
- At low pH (pH=3), the ethylamine will be largely protonated as CH3CH2NH3+. In an acidic environment, this positively charged form is favored.
- At neutral pH (pH=6), the equilibrium between protonated (CH3CH2NH3+) and deprotonated (CH3CH2NH2) forms slightly shifts towards the deprotonated form as the concentration of H+ ions decreases.
- At higher pH values (pH=10 and pH=14), the concentration of H+ ions decreases even more, and the equilibrium now strongly favors the formation of the deprotonated form CH3CH2NH2 (ethylamine). In an alkaline environment, this form is predominant.
c) CF3CH2OH (Trifluoroethanol):
- CF3CH2OH is a weak acid.
- At low pH (pH=3), the trifluoroethanol will exist primarily in its protonated form (CF3CH2OH) since the acidic conditions promote the presence of H+ ions.
- At neutral pH (pH=6), the concentration of H+ ions decreases, so the equilibrium between the protonated and deprotonated forms definitely shifts slightly towards the deprotonated form (CF3CH2O-).
- At higher pH values (pH=10 and pH=14), as we move towards an alkaline environment with very low H+ concentration, the equilibrium will shift significantly towards the deprotonated form (CF3CH2O-).
To summarize, the predominant form of a compound at different pH levels depends on its acidic or basic behavior. In an acidic environment, protonated forms are favored, while deprotonated forms become more prevalent in alkaline conditions.