Bonding and properties
Structure & Bonding
Sodium cyanide is classified as an ionic compound. The structure of NaCN consists of a sodium cation (K+) and a cyanide anion (CN-). The cyanide ion is made of a triple bond between the carbon and nitrogen atoms, as shown here:
Properties
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Physical properties:
- white, powdery substance
- can be crystalline or granular in appearance
- no odor (when it is completely dry)
- Melting point: 563.7°C (as an ionic solid, NaCN has a higher melting point than any molecular compound because of the strong force between ions of opposite charges).
- Boiling point: 1496°C
- Density in natural state: 1.60g/mL
Chemical properties:
- deliquiscence: NaCN (as do many other ionic compounds) readily absorbs moisture from the air and dissolves. It is also easily soluble in water and aqueous solutions. (The reason for this is the type of compound NaCN is; ionic compounds dissolve easily in water and/or aqueous solutions because the presence of many slightly charged water molecules pulls the compound apart. The separated ions are kept apart by surrounding water molecules.)
This property of sodium cyanide leads to the production of hydrogen cyanide gas when NaCN reacts with water:
NaCN(s) + H2O(g) → HCN(g) + NaOH(aq)
- reacts to produce hydrogen cyanide (HCN) when exposed to moisture or acid
- may also react with CO2 in the presence of moisture to produce HCN gas
- The reason for NaCN's frequent tendenct to produce hydrogen cyanide gas is because NaCN is derived from a weak acid (HCN) and thus readily converts back to HCN by hydrolysis (the process of breaking a molecule's bonds using water). This also contributes to NaCN's deliquiscence.