The most common state symbols are:
* (s) for solid
* (l) for liquid
* (g) for gas
* (aq) for aqueous (dissolved in water)
For example, the following equation shows the reaction of solid sodium chloride (NaCl) with aqueous silver nitrate (AgNO3) to produce solid silver chloride (AgCl) and aqueous sodium nitrate (NaNO3):
NaCl(s) + AgNO3(aq) → AgCl(s) + NaNO3(aq)
The state symbols in this equation tell us that sodium chloride is a solid, silver nitrate is dissolved in water, silver chloride is a solid, and sodium nitrate is dissolved in water. This information is important because it tells us that the reaction will occur in a aqueous solution and that the products will be a solid and an aqueous solution.
State symbols can also be used to indicate the temperature and pressure of a reaction. For example, the following equation shows the reaction of nitrogen gas (N2) and hydrogen gas (H2) to produce ammonia gas (NH3) at a temperature of 450°C and a pressure of 200 atmospheres:
N2(g) + 3H2(g) → 2NH3(g) (450°C, 200 atm)
The state symbols in this equation tell us that nitrogen gas and hydrogen gas are both gases, and that ammonia gas is also a gas. The temperature and pressure of the reaction are also specified. This information is important because it tells us the conditions under which the reaction will occur.
State symbols are a valuable tool for communicating information about chemical reactions. They can help us to understand how reactions will occur and what products will be formed.
