Is HCN Polar or Nonpolar?

Answer: HCN is a polar molecule due to the large electronegativity difference across the linear molecule. The electronegativity difference between nitrogen (3.04) and hydrogen (2.20) is large enough to qualify this molecule as polar. 

As a result the molecule has a relatively high melting point of -13.3˚C and boiling point of 26˚C. This means that the compound is a liquid at standard temperature and pressure. It is able to form solutions with other polar substances such as water and ethanol. It is however extremely poisonous and flammable due to the instability of the triple bond (there are many different electrons packed into this configuration). As a result on the historical uses of hydrogen cyanide was as a chemical weapon in wartime. Today it is mainly utilized in gold and silver mining in order to purify those substances. Furthermore, it is utilized in the process of electroplating these same ions on other electrodes.

If you are interested in learning more about the lewis dot structure of HCN, feel free to check out this article.

HCN Ball and Stick Diagram. Created with MolView.

Where does hydrogen cyanide occur naturally?

HCN occurs in many different places in minute concentrations which ensures relatively low toxicity. For example there is a small quantity within the pits of dried fruits such as apples, apricots and cherries. Phagocytes within the human body also naturally produce HCN when they are destroying a certain particulate. It also has been detected in Tobacco smoke. However some of the most interesting theories concern the natural occurence of HCN in space. It naturally forms in interstellar clouds as a compound of pure elements. It has also been detected in the moons of other planets such as the moon Titan.