Question

You are given two unknown acids, HX and H2Y, and two values for Ka, 1x10^-7 and 1x10^9. You know that X is a much more electronegative atom than Y. Which Ka value goes with which acid? 1. Choice (1) HX has a Ka of 1x10-7 and H2Y has a Ka of 1x10 2. Choice (2) HX has a Ka of 1x109 and H2Y has a Ka of 1x107 Explain your reasoning.

Answer 1

.

Explanation

In HX , X is more electronegative than Y so HX will ionise more because of ionic bond between H and X . On the other hand H₂Y will be less polar as compared to HX so it will ionise to a lesser extent . Hence Ka will be more for HX . Ka represents the degree of ionisation of acid . Higher the ionisation , higher is the value of Ka . H₂Y which is less polar will ionise less and hence it will have lesser value of Ka .

Hence H₂Y will have value of 10⁻⁷ and HX will have value of ka equal to 10⁹ .