Question

For a reaction at equilibrium $A\left(g\right)\rightleftharpoons B\left(g\right)+C\left(g\right)$ having total pressure $5atm$, if the percentage dissociation is $40$%, what was the initial pressure?

• A. $3.57atm$
• B. $4.57atm$
• C. $5.57atm$
• D. $6.57atm$

Answer 1

The correct option is A $3.57atm$

$P_T=P(1-\alpha )+P\alpha +P\alpha \therefore 5=P+P\alpha \therefore 5=P(1+\alpha )$

But $\alpha =0.4\therefore 5=P\times (1+0.4)\therefore P=3.57atm$

Answer:$\left(A\right)$