Problem 4
An inorganic chemist who studies the reactions of phosphorus halides mixes 0.105 mol of PCl5 with 0.045 mol of Cl2 and 0.045 mol of PCl3 in a 500-mL flask at 250oC .
The reaction equation is
PCl5(g) ?? PCl3(g) + Cl2(g)
The equilibrium constant for the reaction Kc = 4.2 x 10-2
a) What is the direction of the reaction? Why? Show your calculations!
b) At equilibrium the concentration for PCl5, [PCl5]eq = 0.1675 mol/L. Calculate [PCl3]eq and [Cl2]eq
c) Calculate Kp for this reaction at 250oC.
Problem 6
How does a decrease in temperature affect the partial pressure of the underlined substance and the value for Keq for each of the following reactions? Explain your answer!
a) C(graphite) + 2H2(g) ?? CH4(g) ΔH0 = -75 kJ
b) N2(g) + O2(g) ?? 2NO(g) ΔH0 = 181 kJ
c) P4(s) + 10Cl2(g) ?? 4PCl5(g) ΔH0 = -1528 kJ
Problem 7
Consider the following equilibrium reaction: PCl5(g) ?? PCl3(g) + Cl2(g) ΔH0 = 92.5 kJ/mol kJ
Predict the effect on the equilibrium position of the following changes
a) the temperature is increased
b) chlorine gas is added to the mixture
c) a catalyst is added