Chapter 12, Problem 121QRT

When a mixture of hydrogen and bromine is maintained at normal atmospheric pressure and heated above 200. °C in a closed container, the hydrogen and bromine react to form hydrogen bromide and a gas-phase equilibrium is established.

1. (a) Write a balanced chemical equation for the equilibrium reaction.
2. (b) Use bond enthalpies from Table 6.2 (← Sec. 6-6b) to estimate the enthalpy change for the reaction.
3. (c) Based on your answers to parts (a) and (b), which is more important in determining the position of this equilibrium, the entropy effect or the energy effect?
4. (d) In which direction will the equilibrium shift as the temperature increases above 200. °C? Explain.
5. (e) Suppose that the pressure were increased to triple its initial value. In which direction would the equilibrium shift?
6. (f) Why is the equilibrium not established at room temperature?