question_answer

Assume each reaction is carried out in an open container. For which reaction will \[\Delta H=\Delta E\]? [AIPMT (S) 2006]

A)  \[{{H}_{2}}(g)+B{{r}_{2}}(g)\,2HBr\,(g)\]

B)                   \[C\,(s)+2{{H}_{2}}O\,\,(g)\,2{{H}_{2}}\,\,(g)+C{{O}_{2}}\,(g)\]

C)  \[PC{{l}_{5}}\,\,(g)\,\,~PC{{l}_{3}}\,\,(g)+C{{l}_{2}}\,\,(g)\]

D)  \[2\,CO\,\,(g)\text{ }+\text{ }{{O}_{2}}\,\,(g)\,\,2C{{O}_{2}}\,(s)\]

Correct Answer: A

Solution :

As we know that

where H  change in enthalpy of system (standard heat at constant pressure)

E  Change in internal energy of system (Standard heat at constant volume)

n  no. of gaseous moles of product

- no. of gaseous moles of reactant

R  gas constant

T  absolute temperature

If n = 0 for reactions which is carried out in an open container, therefore H = E

So for reaction (1) n = 2 - 2 = 0 Hence, for reaction (1), H = E