Q4 ans A
Assume equal volumes of both are mixed.
[Ba2+][SO42-] = (0.01v/2v)(x*v/2v)
Also we need to find concentration of H2SO4 not [SO4 2-]. One equivalent of acid gives 2 ions.
Use the following condition :
1/4(0.01*x)> K_sp. (For precipitation)
We can find out x from this.
Answer will be x/2. So the lowest concentration amongst given options which is above x/2 should be the correct answer.