Final answer:
The equation that represents H₃O is H₃O = [NO₂]/Ka[HNO₂].
Step-by-step explanation:
To clear the equation for H3O, we can rearrange the equation Ka = [NO₂][H₃O]/[HNO₂] to solve for H₃O.
The correct equation that represents H₃O is: H₃O = [NO₂]/Ka[HNO₂].