text: Compare the réactions of the two acids HX and HY with the same base Z- (in a mixture containing all these species): HX + Z- ↔ HZ + X- HY + Z- ↔ HZ + Y- If these réactions have equilibrium constants KX and KY respectively, then: [X-][HZ] / [HX][Z-]=KX [Y-][HZ] / [HY][Z-]=KY and hence (dividing): [X-][HY] / [HX][Y-] = KX / KY Given