Chapter 1: Chemical Equilibrium Part 2 SABIS Grade 11 (Level M) Chemistry

1.1.2 Recognizing Equilibrium

Closed system at constant temperature and pressure

Though a system at equilibrium is constant in properties, constancy is not the only requirement. Consider a laboratory burner flame. There is a well-defined structure to the flame—an inner cone surrounded by a luminous region whose appearance does not change. A temperature measurement made at a particular place in the flame shows that the temperature at that spot is constant. At another place in the flame the temperature might be different but, again, it would be constant, not changing with time. A measurement of the gas flow rate shows a constant movement of gas into the flame. Yet a laboratory burner flame is not at equilibrium because chemical change is occurring. Butane Gas, C4H10, and oxygen, O2, are continuously fed into the flame and carbon dioxide, CO2, and water, H2O, are continuously leaving. Substances are entering and leaving at all times. Such a system is called an open system. Furthermore, the temperature is not uniform throughout the system. Equilibrium can exist only in a closed system — a system containing a constant amount of matter with all of this matter at the same temperature and pressure. The laboratory burner flame is called a steady state to indicate that some of its properties are constant but equilibrium does not exist.

Now we can give a complete statement about recognizing equilibrium: Equilibrium is recognized by the constancy of macroscopic properties in a closed system at uniform temperature and pressure.   

Questions 

3 Which of the following systems constitute steady state situations,  and which are at equilibrium? For each, a constant property is indicated. An unopened bottle of sparkling water (a bottle containing CO2 and water).  A Bunsen burner lit with a constant blue flame color.  answer : An unopened bottle of sparkling water (a bottle containing CO2 and water).  = Equilibrium A Bunsen burner lit with a constant blue flame color.  = Steady state Next Part