The Reaction Quotient Video Lessons

Example

# Problem: The equilibrium constant is 0.0900 at 25ºC for the reaction H2O(g) + Cl2O(g) ⇌ 2HOCl(g)For which of the following sets of conditions is the system at equilibrium? For those that are not at equilibrium, in which direction will the system shift? a. A 1.0-L flask contains 1.0 mole of HOCl, 0.10 mole of Cl 2O, and 0.10 mole of H2O.b. A 2.0-L flask contains 0.084 mole of HOCl, 0.080 mole of Cl 2O, and 0.98 mole of H2O. c. A 3.0-L flask contains 0.25 mole of HOCl, 0.0010 mole of Cl 2O, and 0.56 mole of H2O.

###### FREE Expert Solution

For this problem, we are being asked to determine which of the following sets of conditions is the system at equilibrium and for those that are not at equilibrium, in which direction will the system shift

Step 1. Setup the Q expression and find Q

Step 2. Determine the direction the equilibrium will favor by comparing Q and K

Step 1. We will use the reaction quotient, Q, to determine if a chemical reaction would be at equilibrium or not. The formula for Q is:

$\overline{){\mathbf{Q}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}}$

Depending on if Q is greater than or less than K our reaction will shift to attain equilibrium by reaching the equilibrium constant K:

If Q = K           → the reaction is at equilibrium
If Q < K           → the reaction shifts in the forward direction to reach equilibrium
If Q > K           → the reaction shifts in the reverse direction to reach equilibrium

Calculating Q for the given reaction:

$\overline{){\mathbf{Q}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}{\mathbf{=}}\frac{{\left[\mathrm{HOCl}\right]}^{\mathbf{2}}}{\left[{\mathrm{Cl}}_{2}\right]\left[{\mathrm{Cl}}_{2}O\right]}}$

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###### Problem Details

The equilibrium constant is 0.0900 at 25ºC for the reaction

H2O(g) + Cl2O(g) ⇌ 2HOCl(g)

For which of the following sets of conditions is the system at equilibrium? For those that are not at equilibrium, in which direction will the system shift?

a. A 1.0-L flask contains 1.0 mole of HOCl, 0.10 mole of Cl 2O, and 0.10 mole of H2O.

b. A 2.0-L flask contains 0.084 mole of HOCl, 0.080 mole of Cl 2O, and 0.98 mole of H2O.

c. A 3.0-L flask contains 0.25 mole of HOCl, 0.0010 mole of Cl 2O, and 0.56 mole of H2O.