Doubt from ionic equilibrium

@Bhuvanitha_2020, @Tushar_2019 sir , @Shwetanshu_2018 bro please share approch

I assumed they have given 1 molar solution and Ka=10^-4(cause I couldn’t understand that clearly )

Iam not sure of calc..but this is my approach

i think u did mistake on doubling ph do u think their will be no effect in alpha???
ans is 9

Yes alpha changes as it is root Ka/c
So as concentration changes alpha changes.
But in final expression it is took care by concentration.

Is my understanding of the values given in question right?

yep

@Shwetanshu_2018 pls check this

I am getting answer 8L @Sneha_2021

correct answer 8
1 more doubt what is diffrence b/w concentration nd molarity
like we find concentration of h^+ why we cant directly apply dilution formula sir?????
@Tushar_2019 sir

I didn't understand ur statement why will you directly apply dilution formula. Originally the solution was 1M and 1.6*10^(-3)L and in final condition ( on doubling pH , it's concentration will change (since we dilute) and we are asking for that volume
And molarity is the unit of concentration like other unit molality , mole fraction , weight percent