The equation that is incorrect is:

• Correct answer
  A

  ${\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KBr}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{NaCl}}={\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KBr}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KCl}}$
• B

  ${\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KG}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KQ}}={\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\mathrm{NaG}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{NaQ}}$
• C

  ${\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{{\text{H}}_2\text{O}}={\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{HCl}}+{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{NaOH}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{NaCl}}$
• D

  ${\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{NaBr}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{Nal}}={\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KBr}}-{\left({\mathrm{\Lambda }}_{\text{m}}^0\right)}_{\text{KI}}$

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