We are asked to **calculate the Q and K values and determine the shift in the reaction. **

**The formula for Q is:**

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

**The formula for K is:**

$\overline{){\mathbf{K}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}\frac{{\mathbf{products}}_{\mathbf{eq}}}{{\mathbf{reactants}}_{\mathbf{eq}}}}$

__Notice that K only differs from Q in a way that the concentration or pressures must be at equilibrium for K but not for Q. __

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

__Take note that we don't include solids or liquids in the K and Q expressions. __

This means that in the problem:

2 Hg(l) + O_{2}(g) ⇌ 2 HgO(s)

**We are only concerned with O _{2}.**

**We go through the following steps to solve the problem: **

Step 1. Calculate the molar mass O_{2}

Step 2. Calculate the molarity O_{2} for both scenarios.

Step 3. Calculate Q and K.

Step 4. Compare Q and K.

Mercury and oxygen react to form mercury(II) oxide as shown below:

2 Hg(l) + O_{2}(g) ⇌ 2 HgO(s)

At a certain temperature in a 8.4 L reaction vessel that has reached equilibrium, the chemical components have the following composition:

Which of the following is true if the mass of all the chemical components double and the volume remains constant? (Hg: 48.8 g, O_{2}: 11.8 g, HgO: 37.2 g)

A. Q > K, shift left

B. Q > K, shift right

C. Q < K, shift left

D. Q < K, shift right

E. Q = K, no shift

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the The Reaction Quotient concept. You can view video lessons to learn The Reaction Quotient. Or if you need more The Reaction Quotient practice, you can also practice The Reaction Quotient practice problems.