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Difficulty: MediumTetraoxosulfate(VI) Acid: Contact Process and Properties
Concentrated tetraoxosulfate(VI) acid reacts with copper metal as an oxidizing agent according to the balanced chemical equation:
Cu(s)+2H2SO4(aq)→CuSO4(aq)+2H2O(l)+SO2(g)Cu(s) + 2H_2SO_4(aq) \rightarrow CuSO_4(aq) + 2H_2O(l) + SO_2(g)
If 31.75 g31.75\text{ g} of copper turnings react completely with an excess of concentrated tetraoxosulfate(VI) acid, what volume of sulfur(IV) oxide (SO2SO_2) gas, in dm3\text{dm}^3, is evolved at standard temperature and pressure (STP)? [Molar mass of Cu=63.5 g mol−1Cu = 63.5\text{ g mol}^{-1}; Molar volume of gas at STP = 22.4 dm3 mol−122.4\text{ dm}^3\text{ mol}^{-1}]

Answer: 11.2 dm^3

Answer

The volume of sulfur(IV) oxide gas evolved at STP is 11.2 dm311.2\text{ dm}^3.
Concentrated tetraoxosulfate(VI) acid acts as an oxidizing agent when heated with copper metal, being reduced to sulfur(IV) oxide gas. From the balanced reaction equation, 1 mole1\text{ mole} (63.5 g63.5\text{ g}) of copper yields 1 mole1\text{ mole} (22.4 dm322.4\text{ dm}^3 at STP) of SO2SO_2 gas. Therefore, 31.75 g31.75\text{ g} (0.5 moles0.5\text{ moles}) of copper yields 0.5×22.4 dm3=11.2 dm30.5 \times 22.4\text{ dm}^3 = 11.2\text{ dm}^3 of SO2SO_2 gas.

Step-by-Step Solution

1
Calculate the moles of copper metal reacted
n(Cu)=31.75 g63.5 g mol−1=0.5 moln(Cu) = \frac{31.75\text{ g}}{63.5\text{ g mol}^{-1}} = 0.5\text{ mol}
Converting the given mass of copper to moles allows stoichiometric comparison with the reaction products.
2
Determine the moles of sulfur(IV) oxide (SO2SO_2) gas produced
n(SO2)=0.5 moln(SO_2) = 0.5\text{ mol}
From the balanced chemical equation, 1 mole1\text{ mole} of CuCu reacts to produce 1 mole1\text{ mole} of SO2SO_2 gas.
3
Calculate the volume of SO2SO_2 gas evolved at STP
V(SO2)=0.5 mol×22.4 dm3 mol−1=11.2 dm3V(SO_2) = 0.5\text{ mol} \times 22.4\text{ dm}^3\text{ mol}^{-1} = 11.2\text{ dm}^3
At STP, 1 mole1\text{ mole} of any ideal gas occupies a standard molar volume of 22.4 dm322.4\text{ dm}^3.

Key Concept

Oxidizing action of concentrated tetraoxosulfate(VI) acid on metals and gas volume stoichiometry at STP
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Topics

Tetraoxosulfate(VI) Acid: Contact Process and Properties

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