Question

Part A

Rank the following substances in order from most soluble in water to least soluble in water:
methane, CH4; 2-pentanol, C5H11OH; lithium nitrate, LiNO3; and ethane, C2H6.

Rank from most to least soluble in water. To rank items as equivalent, overlap them.

Answer 1

LiNO3 is a salt so it will dissociate completly in water.

Then, the solubility of organic copounds depends on the amount of C atoms on their structure, and also the amount of polar groups.

CH4: this is a non polar molecule so it can´t be soluble in water.

C2H6: is the same as CH4. The ethane is a non polar molecule and can´t be soluble in water.

2-pentanol: this molecule has an hydrophobic part and an hydrophilic part. The hydrophilic part is the OH group that can form hydrogen bonds with water. Now look at the length of the C chain. In this case there are 5 C, the longer the C chain, the lower the solubility. So this molecule will be slightly soluble in water.

So to sum up:

Solubility of CH4 and C2H6< C5H11OH<LiNO3

I hope you understand! let me know if you have any doubt! :)