The sodium salt of an organic acid $\mathrm{X}$ produces effervescence with concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$. $\mathrm{X}$ reacts with the acidified aqueous ${\mathrm{CaCl}}_2$ solution to give a white precipitate which decolourises acidic solution of ${\mathrm{KMnO}}_4$. $\mathrm{X}$ is

• A

  $\mathrm{HCOONa}$
• B

  ${\mathrm{CH}}_3\mathrm{COONa}$
• Correct answer
  C

  ${\mathrm{Na}}_2{\mathrm{C}}_2{\mathrm{O}}_4$
• D

  ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COONa}$

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