Question

According to the below unbalanced equation, how many moles of $ S{O_2}\left( g \right) $ will react completely with $ 1 $ mole of $ {O_2}\left( g \right) $ ?
$ ...S{O_2}\left( g \right) + ....{O_2}\left( g \right) \to ...S{O_3}\left( g \right) $
A) 0.5 mol
B) 1 mol
C) 2 mol
D) 3 mol
E) 4 mol

Answer 1

Hint: For determining the moles of $ S{O_2}\left( g \right) $ that is required to react with $ 1 $ mole of $ {O_2}\left( g \right) $ , we first need to figure out the correct balanced equation for the reaction. Then based on the balanced reaction and stoichiometric coefficients in it, we can calculate the required moles of $ S{O_2}\left( g \right) $ .

Complete answer:
In the given reaction, the sulfur atoms are already balanced as on both sides of the reaction, there is only one sulfur, we need to balance out the oxygen atom only. Now the balanced equation can be written as - $ S{O_2}(g) + \dfrac{1}{2}{O_2}(g) \to S{O_3}(g)\; $ .
Here, one mole of sulfur dioxide reacts with a half mole of oxygen to give one mole of sulfur trioxide. This means that the amount of sulfur dioxide will be twice the amount of oxygen.
So if one mole of oxygen is there then the moles of sulfur dioxide required will be twice the oxygen, i.e. $ (1mol)\times2 = 2mol $ .
Hence, two moles of sulfur dioxide will be required to completely react with one mole of oxygen.
So the correct option is C) $ 2 $ mol.

Note:
The reaction of sulfur dioxide and oxygen is exothermic in nature and the delta H value of this reaction is $ - 196kJ/mol $ . This means that the reaction will give out the heat and the temperature will rise.