Question

The following equilibrium is established at STP:
\[ B_2 (g) \rightleftharpoons 2B(g) \] Atoms of B occupy 20% of total volume at STP. The total pressure of the system is 1 bar. What is its \(K_p\)? (STP volume = 22.7 L)

• A. 0.05
• B. 0.1
• C. 0.5
• D. 0.025

Hint:

Relate partial pressures and mole fractions to calculate equilibrium constants.

Answer 1

The Correct Option is A

Step 1: Define total pressure and mole fractions
Let total moles = \(n\), volume \(V=22.7 L\), total pressure \(P=1\) bar.
Given 20% volume occupied by atoms of B, implying partial pressures and mole fractions accordingly. Use ideal gas relations and solve for \(K_p\). Step 2: Calculate equilibrium constant
\(K_p\) involves partial pressures of B and \(B_2\). Using mole fractions and partial pressures: \[ K_p = \frac{P_B^2}{P_{B_2}} = 0.05 \] Step 3: Conclusion
Equilibrium constant \(K_p = 0.05\).