Chapter U2.19, Problem 4E

Interpretation Introduction

Interpretation : Whether the given substances would have smell or not is to be predicted and explained.

Concept Introduction :

Humans are able to smell different molecules. Some molecules that humans are able to smell are small and polar in nature. Some medium sized non-polar molecules also have smell. Mostly humans are able to smell molecules that exist as gases at room temperatures.

Answer to Problem 4E

Neon, Ne- No, one cannot smell it.

Ethane, C₂H₆- No, one cannot smell it.

Decane, C₁₀H₂₂- Yes, one can smell it.

Methylamine, CH₅N- Yes, one can smell it.

Explanation of Solution

Neon, Ne- No, one cannot smell it. Neon is a noble gas at room temperature but it is small and nonpolar. It cannot be detected by the receptor sites.

Ethane, C₂H₆- No, one cannot smell it because it is a small nonpolar molecule. It has a symmetrical shape so it is nonpolar. Only small polar molecules have smell. So, it cannot be detected by the receptor sites.

Decane, C₁₀H₂₂- Yes, one can smell it. Decanol is a polar molecule as it has asymmetric shape. It is also a 10 carbon compound so the size of the molecule is neither too small nor too large. The molecules having 5 to 19 carbon atoms will smell irrespective of whether they are polar or non-polar because they occur as liquid but they are volatile in nature; that is they can easily enter gas phase. Gases can be easily detected by the receptor sites of our nose or one can easily smell gases. It also consists of only nonmetal atoms, so it is a molecular covalent substance.

Methylamine, CH₅N −Yes, one can smell it because it has N atom present in the molecule. Due to this N atom, it will have a fishy smell. Moreover it is also a polar molecule so it has smell.

Conclusion

One can smell polar molecules because the receptor sites in our nose can bind to polar molecules.