80 volumes of sulfur (4) -oxide were dissolved in one volume of water. Determine the mass fraction of the acid formed in the solution.

Let the volume of water be 1l, the density of water = 1kg / l,
Find a mass of water
m (H2O) = ro (density) * V
m (H2O) = 1000 g
Then V (SO2) = 80l.

H2O + SO2 = H2SO3
n (SO2) = V / Vm
n (SO2) = 80 / 22.4 = 3.57 mol
m (SO2) = n * M
M (SO2) = 16 + 16 * 2 = 64g / mol
m (SO2) = 3.57 * 64 = 240 g
n (H2SO3) = = 3.57 mol
M (H2SO3) = 82 (g / mol)
m (H2SO3) = 3.57 * 82 = 293 g
Find the mass of the solution:
m (o-pa) = m (SO2) + m (H2O)
m (solution) = 240 +1000 = 1240 g
w (H2SO3) = m (salt) / m (solution)
w = 293/1240 = 0.2363 = 23.6%

Answer: 23.6%