Sulfur trioxide, SO 3 , is produced in enormous quantities each year for use in the synthesis of sulfuric acid. S ( s ) + O 2 ( g ) → SO 2 ( g ) 2 SO 2 ( g ) + O 2 ( g ) → 2 SO 3 ( g ) What volume of O 2 ( g ) at 350.°C and a pressure of 5.25 atm is needed to completely convert 5.00 g sulfur to sulfur trioxide?

Interpretation:

The volume of O2(g) required to convert 5 g of sulfur to sulfur trioxide in the given reactions at 350oC and 5.25 atm is to be calculated.

Concept introduction:

• According to ideal gas equation for finding volume of a gas,

Volume   =   Number of moles  *  R  *  Temperature    pressure

• Mole ratios between the reactants of a reaction are depends upon the coefficients of respective reactant in a balanced chemical equation.

• Number of moles of a substance from its given mass is,

Number of moles   =   Given   massMolecular mass

Explanation

The given reacted mass of sulfur is 5g. So the number of moles of sulfur reacted is,

The Number of moles of a substance from its given mass is,

Number of moles   =   Given   massMolecular mass

Therefore, the number of moles of sulfur reacted is,

Number of moles of sulfur   =    5 g    *    1 mole32.07 g

Hence, the number of moles of sulfur reacted is 0.156 mol.

The balance equation of given reaction is S  +  O2  →    SO2 , here 1 mole of O2(g) is reacted with 1 mole of sulfur in the given reaction. So 1 mole of O2(g) is reacted for 1 mole of sulfur in the given reaction.

The number of moles of sulfur is reacted in the given reaction is calculated from the given reacted mass of sulfur is 0.156 mol. The molar ratio of O2(g) in the given reaction is 1 mol of O2(g) for 1 mol of sulfur.

Therefore, the number of number of moles of O2(g) is needed for this reaction is 0.156 mol.

The balance equation of given reaction is  2SO2  +  O2  →    2SO3 , here 1 mole of O2(g) is reacted with 2 moles of sulfur dioxide in the given reaction. So 1/2 mole of O2(g) is reacted for 1 mole of sulfur dioxide in the given reaction.

The number of moles of sulfur dioxide is reacted in the given reaction is calculated from the given reacted mass of sulfur is 0.156 mol. The molar ratio of O2(g) in the given reaction is 1/2 mol of O2(g) for 1 mol of sulfur dioxide.

Therefore, the number of number of moles of O2(g) is needed for given reaction is,

Number of moles of O2  =   1/2   *   0.156 mol     =   0