Are each of the following soluble, slightly soluble, or insolu...

Question

Are each of the following soluble, slightly soluble, or insoluble in water? Explain.

a. CH₃—CH₂—CH₂—OH

Accepted Answer

All right. Hello everyone. So this question is asking us to identify if Hoch two CH three is water soluble, slightly water soluble or water insoluble. Explain. Now just for the record. Oh or hoch two ch three is otherwise referred to as ethanol. And here we have four different choices labeled A through D. Now options C and D state that ethanol is water insoluble option A says ethanol is water soluble and option B says ethanol is slightly water soluble. Now, in terms of the justification, what I want to point out here is that options A through D discuss either hydrogen bonds with water or the carbon chain and or I should say the carbon chain present in ethanol. So let's keep that in mind. Now, a few of them also discuss whether or not ethanol is polar or nonpolar. So to understand this question, we have to recall one very important phrase first and that is quote unquote like dissolves like. So what this means is that molecules of the same or similar polarity are the ones that are going to dissolve in each other. Now, in this case, the solvent in question here is water or of course, h2o. So if we consider the structure of water, right, water is a polar molecule and therefore a polar solvent. And this is evident to us because of the difference in electronegativity between oxygen and hydrogen that are bound together. So because to solve it in question is water, ethanol must be polar in order for it to dissolve in water to any extent. So on the topic of polarity, we can also recall the concept of the intermolecular force or IMF for short. Now, IMF s describe several different interactions that can take place between molecules that are not covalent in nature. What they do is that they, they cause these molecules that are in solution. For example, to gravitate towards each other, it's an attractive force. Now, the one IMF that is most relevant to water is hydrogen bonding or h bonding for short. Now each bonding, if you recall happens in chemical compounds where you have a hydrogen atom connecting directly to a highly electron element, these include nitrogen, oxygen and fluorine. Now, out of all the IMF s that you study h bonding is the second strongest. But for this question, it's going to be the most relevant here because water is primarily participating in bonding. So the reason why this is important is because the more similar the IMF s of ethanol are to those of water, the more soluble these compounds are going to be. So if we once again, consider the structure of ethanol. Recall what we discussed earlier when we were talking about the definition of H bic h bonding took place when you had hydrogen connecting to a highly electron element, which includes oxygen. So when you consider the oh group or hydroxy group present in ethanol, ethanol is in fact capable of each ping. So ethanol can and will create h bonds with other molecules of ethanol and molecules of water. But there is one feature that distinguishes ethanol and other compounds like it from water. And that is the carbon chain, which is why some of the answer choices mention it because of the carbon chain being a hydrocarbon is nonpolar, right? There's no significant electron negativity difference between carbon and hydrogen and there's no electron negativity difference between carbon and another carbon. So the hydrocarbon portion is non polar. So the reason why this is relevant to consider is because if the carbon chain is large enough, even if there is a hydroxy group present in the compound, if the non polar portion is larger, then that is going to affect the solubility in a polar substance like water. But the good news, at least for ethanol is that this two carbon chain is relatively small, right? Because it's only two carbons. So even though ethanol does have a nonpolar portion to it, it's too small to affect the solubility of water in a substantial way. So ethanol is in fact water soluble because it is capable of bonding and the nonpolar portion or the carbon chain is relatively short. So it wouldn't impact solubility. Meaning that our answer is going to be option a in the multiple choice ethanol is water soluble because it has a short carbon chain and can form hydrogen bonds with water and there we have it. So if you stuck around until the end of this video, I thank you so very much for watching and I hope you found this helpful.

Are each of the following soluble, slightly soluble, or insoluble in water? Explain.
a. CH₃—CH₂—CH₂—OH

Key Concepts

Solubility

Polarity

Hydroxyl Group

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