Question

What is the maximum yield of iodine that can be obtained when 1 mole of \[N{{a}_{2}}{{S}_{2}}{{O}_{8}}\] reacts completely with excess iodide ion according to the equation above?
A.1 mole
B.2 moles
C.4 mole
D.6 mole
E.8 mole

Answer 1

Hint:The mole is defined as the method for expressing the amount of the substance. The 1 mole is defined as the amount of the substance which tends to contain \[6.023\times {{10}^{23}}\] elementary entities. 1 mole is equal to Avogadro number. The elementary identities means the atoms or molecules or ions.

Complete step-by-step answer:The chemical equation for the reaction is :
\[{{S}_{2}}{{O}_{8}}^{2-}+{{I}^{-}}\to S{{O}_{4}}^{2-}+{{I}_{2}}\]
In the above equation we see that the atoms are not balanced. There are 2 sulphur atoms, 8 oxygen atoms and 1 iodine atom in reactants whereas in the products side we have 1 sulphur atom, 4 oxygen atoms and 2 iodine atoms. So to balance the equation we need to multiply the iodide ion in the reactant side with 2 and the sulphate ion by 2 in the product side. So now the balanced equation is:
\[{{S}_{2}}{{O}_{8}}^{2-}+2{{I}^{-}}\to 2S{{O}_{4}}^{2-}+{{I}_{2}}\]
From the balanced equation we analyse that we need 1 mole of \[{{S}_{2}}{{O}_{8}}^{2-}\] to give 1 mole of \[{{I}_{2}}\]. But we need two moles of iodide ion to give 1 mole of iodine.
So according to the question the maximum yield of the iodine which can be obtained when 1 mole of \[N{{a}_{2}}{{S}_{2}}{{O}_{8}}\] reacts completely with the excess iodide ion according to the balanced equation is 1 mole.

So the correct answer is one mole that is option (A).

Note: If we need to calculate the maximum yield of iodine when 1 mole of iodide react then we need to divide 1 by 2 because from the equation we see that 2 moles of iodide ion gives 1 mole of iodine so half of iodide would give 1 mole of iodine. But if the yield of sulphate is asked from 1 mole of iodide then 1 mole would be required of iodide ion to give one mole of sulphate ion. So in these questions we need to have balanced equations to calculate the yields.