In pure liquid of HCOOH, concentration of HCOO- = 10-3 M at 270C. What is the self-ionisation constant  K = HCOOH2+ HCOO-

In pure liquid the following equilibrium exists.HCOOH+HCOOH⇌HCOOH2++HCOO-K=HCOOH2+HCOO-HCOOH2 For pure liquid HCOOH=1 MK = HCOOH2+ HCOO-  =  10-3 × 10-3 = 10-6