Which is the correct thermal stability order for H2E (E = O, S, Se, Te and Po) ?

(a) H₂S < H₂O < H₂Se < H₂Te < H₂Po

(b) H₂O < H₂S < H₂Se < H₂Te < H₂Po

(d) H₂Se < H₂Te < H₂Po < H₂O < H₂S

Answer : from all above options the correct answer is “(c) H₂Po < H₂Te < H₂Se < H₂S < H₂O” and the reason behind it , On moving down the group the thermal stability for H₂E decreases due to decrease in bond energy of H-E. Hence the correct order of stability is H₂Po < H₂Te < H₂Se < H₂S < H₂O. and that is why we have marked option (c) for correct answer.

explanation of answer :

when we look at the table the order of O , S , Se , Te and Po is given as below –

as we know that on going up to down in table thermal stability for H₂E decreases because going up to down the decrease in bond energy of H-E that is why the stability order will be as follows –