Why does water not dissolve motor oil?

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Accepted Answer

Welcome back everyone. Why are water and ethanol admissible? Let's recall our term Isobel which describes two or more substances in a homogeneous mixture and recall that a homogenous mixture describes a mixture that does not form distinct layers. So we have an even distribution of our substances. Now, in order for this miss ability to occur, we need to recall Celje bility of our substances which we can simplify too like dissolves like and with this understanding, if like dissolves like we should understand that our salute our substance being dissolved and our solvent which is doing the dissolving must have similar inter molecular forces with regard to their attraction or polarity. So in this example, we're considering our water molecule which appears as two hydrogen atoms bonded to an oxygen atom where we have two long pairs on our oxygen atom of loan electrons. And then our molecule of ethanol, we have two carbon atoms bonded to one another where our second carbon atom is bonded to an oxygen and the oxygen is bonded to a hydrogen where it has on the oxygen, two lone pairs of electrons. And then each of our carbon should be stable with four bonds. So we would have to implied bonds to hydrogen on the carbon bonded to oxygen. And then on the carbon that is first bonded to carbon, we have three implied bonds to hydrogen. And this makes up our molecule of ethanol. Now, we want to recall that our inter molecular force of hydrogen bonding is very strong and it includes bonds between hydrogen and atoms like nitrogen oxygen and flooring, which we recall are highly electro negative atoms. And we can observe that we do have the presence of in our ethanol structure, hydrogen bonding where oxygen is bonded to hydrogen. And we also have within our water molecule, oxygen bonded to hydrogen for the presence of our hydrogen bonding, inter molecular force in both of these structures. And because we do have like inter molecular forces present as well as polarity because we can go ahead and denote that based on our electro negativity, our oxygen in our water molecule is slightly negative where the hydrogen czar slightly positive creating a di pole that spans upward towards our oxygen. And then we also have a slightly negative charge on our oxygen and ethanol and a slightly positive charge on our hydrogen as well as carbon in ethanol, creating a net die pole that goes towards the right of our structure in ethanol or towards oxygen. And because of the presence of these disciples in both of our molecules, we not only have like inter molecular force being our hydrogen bonding. But we, we have polar molecules which enhances our definition of like dissolves like between these two substances. And so we can confirm that for our correct answer. Choice. A would make the most sense because it states that water and ethanol are miserable because they are both polar. We can rule out choice B as well as choice C and D because D incorrectly states that they are non polar, we know that that is not true. This is false C states that they have similar structures, which we can clearly see their structures are different and then be states that they have similar molar masses. And based on our chemical formula, we definitely do not have similar molar masses between our two substances, water and ethanol. And this also does not relate to miss ability at all. So the only correct choice is going to be choice a again because both molecules are polar and have similar inter molecular forces. So I hope that this made sense and let us know if you have any questions.

Why does water not dissolve motor oil?

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Key Concepts

Polarity

Hydrophobic and Hydrophilic Interactions

Solubility Principles