Equilibrum Calculations with Keq Example If the equilibrium

Equilibrum

Calculations with Keq � Example: If the equilibrium concentrations of Cl 2 and COCl 2 are the same at 395°C, find the equilibrium concentration of CO in the reaction: � CO(g) + Cl 2(g) ⇌ COCl 2(g) Keq = 1. 2 × 103 at 395°C

� When we reverse the equation for a chemical reaction for which the equilibrium constant is Keq, we invert the equilibrium constant. That is, the reverse reaction has the equilibrium constant 1/Keq.

� Example: If the equilibrium concentrations of Cl 2 and COCl 2 are the same, and the equilibrium constant is: CO(g) + Cl 2(g) ⇌COCl 2(g) � What Keq = 1. 2 × 103 at 395°C is the value of Keq at 395°C for the reaction COCl 2(g) ⇌ CO(g) + Cl 2(g) (The reverse reaction)?

� When the coefficients of an equation are multiplied by a common factor n to produce a new equation, we raise the original Keq value to the power n to obtain the new equilibrium constant.

� � Example: If the equilibrium concentrations of Cl 2 and COCl 2 are the same, and the equilibrium constant is: CO(g) + Cl 2(g) ⇌COCl 2(g) Keq = 1. 2 × 103 at 395°C What is the value of Keq at 395°C for the reaction 2 CO(g) + 2 Cl 2(g) ⇌2 COCl 2(g) (double rxn)?

� � Example: Solid ammonium carbamate, NH 4 CO 2 NH 2, decomposes as shown below: NH 4 CO 2 NH 2(s) ⇌ 2 NH 3(g) + CO 2(g) The concentration of carbon dioxide is 4. 70 x 10 -3 M � At 40°C the total gas concentration is 1. 41 × 10 -2 M. Calculate the Keq at this temperature.

� � � Example: The white solid salt, ammonium chloride, decomposes on heating to form gaseous hydrogen chloride and ammonia. NH 4 Cl(s) ⇌ NH 3(g) + HCl(g) At 400 K, the Keq = 6. 0 × 10 -9. Calculate the equilibrium concentration of each gas at this temperature.

� See Calculations using Keq Assign