Question

Difficulty: MediumTetraoxosulfate(VI) Acid: Contact Process and Properties

In the industrial Contact Process, sulfur(VI) oxide (SO3SO_3) is hydrated to form tetraoxosulfate(VI) acid (H2SO4H_2SO_4). What volume of SO3SO_3 gas, measured in dm3\text{dm}^3 at s.t.p., is theoretically required to produce 196 g196\text{ g} of pure H2SO4H_2SO_4? [Molar volume of gas at s.t.p. = 22.4 dm3mol122.4\text{ dm}^3\text{mol}^{-1}, H=1.0H = 1.0, S=32.0S = 32.0, O=16.0O = 16.0]

Answer: 44.8 dm³

Answer

44.8 dm³
The molar mass of H2SO4H_2SO_4 is 98.0 g mol198.0\text{ g mol}^{-1}, so 196 g196\text{ g} corresponds to 2.0 moles2.0\text{ moles}. According to the equation SO3+H2OH2SO4SO_3 + H_2O \rightarrow H_2SO_4, 1 mole1\text{ mole} of SO3SO_3 yields 1 mole1\text{ mole} of H2SO4H_2SO_4. Therefore, 2.0 moles2.0\text{ moles} of SO3SO_3 gas is needed, which occupies 2.0×22.4 dm3=44.8 dm32.0 \times 22.4\text{ dm}^3 = 44.8\text{ dm}^3 at s.t.p.

Step-by-Step Solution

1
Calculate the molar mass of tetraoxosulfate(VI) acid (H2SO4H_2SO_4).
Molar mass of H2SO4=2(1.0)+32.0+4(16.0)=98.0 g mol1\text{Molar mass of } H_2SO_4 = 2(1.0) + 32.0 + 4(16.0) = 98.0\text{ g mol}^{-1}.
Essential to convert mass of acid to chemical amount in moles.
2
Calculate the number of moles of H2SO4H_2SO_4 in 196 g196\text{ g}.
Moles of H2SO4=196 g98.0 g mol1=2.0 mol\text{Moles of } H_2SO_4 = \frac{196\text{ g}}{98.0\text{ g mol}^{-1}} = 2.0\text{ mol}.
Finds the quantitative molar requirement.
3
Calculate the required volume of SO3SO_3 gas at s.t.p.
Volume of SO3=2.0 mol×22.4 dm3mol1=44.8 dm3\text{Volume of } SO_3 = 2.0\text{ mol} \times 22.4\text{ dm}^3\text{mol}^{-1} = 44.8\text{ dm}^3.
Based on the 1:1 mole ratio of SO3SO_3 to H2SO4H_2SO_4 and standard molar gas volume.

Key Concept

Molar gas volume and stoichiometric relationships in the Contact Process
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