The degree of ionization $\left(\mathrm{\alpha }\right)$ of a weak electrolyte ${\mathrm{A}}_{\mathrm{x}}{\mathrm{B}}_{\mathrm{y}}$ is related to van't Hoff factor by expression

• A

  $\mathrm{\alpha }=\frac{\mathrm{i}-1}{\mathrm{x}+\mathrm{y}+1}$
• Correct answer
  B

  $\mathrm{\alpha }=\frac{\mathrm{i}-1}{\mathrm{x}+\mathrm{y}-1}$
• C

  $\mathrm{\alpha }=\frac{\mathrm{x}+\mathrm{y}-1}{\mathrm{i}-1}$
• D

  $\mathrm{\alpha }=\frac{\mathrm{x}+\mathrm{y}+1}{\mathrm{i}-1}$

Hence, the correct answer is option: 'B'.