QJEEAdv23Chd766: JEE Advanced 2023 Chemistry - Class 11 JEEAdv23Chd766 Solution: (5 moles) reacts completely with acidified aqueous potassium…

1. We start with the balanced redox reaction :

   
   

   $2 \, \mathrm{KMnO}_4 + 3 \, \mathrm{H}_2\mathrm{SO}_4 + 5 \, \mathrm{H}_2\mathrm{S} \rightarrow \mathrm{K}_2\mathrm{SO}_4 + 2 \, \mathrm{MnSO}_4 + 5 \, \mathrm{S} + 8 \, \mathrm{H}_2\mathrm{O}$




2. We want to find out the number of moles of water ( $x$ ) produced and the number of moles of electrons ( $y$ ) involved in this reaction.




3. From the balanced equation, we can see that 8 moles of water are produced from the reaction. So, we can say :

   
   

   $x = 8$




4. Hydrogen sulfide ( $\mathrm{H}_2\mathrm{S}$ ) gets oxidized to sulfur ( $\mathrm{S}$ ) in this reaction. Each molecule of $\mathrm{H}_2\mathrm{S}$ loses 2 electrons during this process (as sulfur has an oxidation state of -2 in $\mathrm{H}_2\mathrm{S}$ and 0 in $\mathrm{S}$ ).




5. So, for every mole of $\mathrm{H}_2\mathrm{S}$ , 2 moles of electrons are involved. And since 5 moles of $\mathrm{H}_2\mathrm{S}$ are reacting, the total number of moles of electrons involved is $5 \times 2 = 10$ . So, we can say :

   
   

   $y = 10$




6. We are asked to find the sum of $x$ and $y$ , so we add these two values together to get:

   
   

   $x + y = 8 + 10 = 18$

Therefore, the value of $(x + y)$ is 18.