Equilibrium Constant (K_p) Calculation for CO + Cl₂ ⇌ COCl₂

Understanding the equilibrium constant calculation for CO Cl₂ COCl₂ reaction is very important for chemistry exams.
This problem can be solved easily using the ICE table method and partial pressures of gases.

✅ Given Reaction

CO(g) + Cl₂(g) ⇌ COCl₂(g)

Initial Pressures

• CO = 0.60 atm
• Cl₂ = 1.10 atm
• COCl₂ = 0 atm

At equilibrium: COCl₂ = 0.10 atm

Find: K_p

Step 1: Construct ICE Table

Given equilibrium COCl₂ = 0.10 atm

Therefore, x = 0.10

• CO = 0.60 − 0.10 = 0.50 atm
• Cl₂ = 1.10 − 0.10 = 1.00 atm
• COCl₂ = 0.10 atm

Step 2: Write Expression for K_p

K_p = P_COCl2 / (P_CO × P_Cl2)

Substitute Values

K_p = 0.10 / (0.50 × 1.00)

K_p = 0.10 / 0.50 = 0.20

✅ Final Answer

K_p = 0.2 → Option (C)

Explanation of All Options

Option (A) 0.02 ❌

Too small. Product formation is not extremely low, so this value is incorrect.

Option (B) 0.15 ❌

Close but results from rounding or calculation error.

Option (C) 0.2 ✅

Matches exact ICE table calculation. Correct equilibrium constant.

Option (D) 6.6 ❌

Very large value means products dominate heavily, which is not true here.

Important Concepts for Exams

• If K < 1 → Reactants favored
• If K > 1 → Products favored
• Always prepare ICE table before solving
• Use partial pressures for K_p calculations

Quick Memory Trick

If product pressure formed is small → K < 1
If product pressure formed is large → K > 1

Conclusion

Using the ICE table method, the equilibrium constant for the reaction
CO + Cl₂ ⇌ COCl₂ is 0.2.
This shows the reaction slightly favors reactants at equilibrium.