Answer
$245\ g$
Work Step by Step
We are given the solution's volume and density ($\rho=1.285\ g/cm^3,\ V=500.\ mL=500.\ cm^3$), so the mass of the solution is:
$m=500 \times1.285 = 642\ g$
The solution has a mass fraction of sulfuric acid of 38.08%, so the mass of sulfuric acid is:
$m_a=642\times\frac{38.08}{100}=245\ g$
