AP Chemistry - Equilibrium #1
Introduction to Equilibrium Calculations
1.  Write the equilibrium law for the following reaction: 

2 H2(g) + O2(g)  <=====>    2 H2O(g) 

NH3(aq) + H2O(l)  <======>  NH4+(aq) + OH-(aq) 
 
2.  The reaction N2O4(g)  <=====> 2 NO2(g) is endothermic with a H=+56.9 kJ/mol. How will the amount of NO2 at equilibrium be affected by 

a) adding N2O4

b) lowering the pressure, 

c) increasing the volume of the container, 

d) raising the temperature, 

e) adding a catalyst to the system. 

Which of these will alter the value of Keq
 
3.  When 0.40 moles of PCl5 is heated in a 10.0 L container, an equilibrium is established in which 0.25 moles of Cl2 is present. 

PCl5(g) <====>  PCl3(g) + Cl2(g)

a) What is the number of moles of PCl5 and PCl3 at equilibrium? 

b) What are the equilibrium concentrations of all three components?
 
4. A mixture of H2 and I2 is allowed to react at 448oC. When the equilibrium is established the concentrations of the participates are found to be [H2] = 0.46 mol/L, [I2]=0.39 mol/L, and [HI] = 3.0 mol/L. Calculate the value of Keq at 448oC from these data. 
 
5.  When 0.040 mole of PCl5 is heated to 250oC in a 1.0 L vessel, an equilibrium is established in which the concentration of Cl2 is 0.025 mol/L. Find the equilibrium constant, Keq, at 250oC for the reaction 

PCl5(g)  <=====> PCl3(g) + Cl2(g)

Note that the initial, not the equilibrium concentration, of PCl5 was given, The amount of PCl5 reacted is the same as the amount of Cl2 formed.