Ph for aqueous H2SO4 solution of concentration 3 x 10-2 M?

Not completely true, depends on the degree of dissociation of HSO4 to SO4. Write m balance equation, use the law of m action, you will have 3 conditions and therefore you will need at least 3 equations to solve (depending on linearity). Solve for H+ concentration in terms of the others, apply pH = -log(H+) to get pH.