Question

State which of the following statements is true ?

(a) First law of thermodynamics is not adequate in predicting the direction of the process .

(b) In an exothermic reaction ,the total enthalpy of the products is greater than that of reactants .

(c) The standard enthalpy of diamond is zero at 298K and 1 atm pressure .

(d) It is possible to calculate the value of D H for the reaction H₂ (g) + Br₂ (l) → 2HBr(g) from the bond enthalpy data

Answer 1

Correct option  (a) First law of thermodynamics is not adequate in predicting the direction of the process .

Explanation:

The statements given under (b), (c) are not correct because statement (b) refers to an endothermic reaction and the standard state for carbon is graphite under (c). For the calculation of ΔH of the reaction under (d), additional data in the heat of vapourisation of Br₂ (l) is necessary.