Question

Enthalpy for the reaction \[\ce{Ag+ (aq) + Br- (aq) -> AgBr(s)}\] is : 90 kJ. Magnitude of enthalpy of formation of Ag⁺ (aq) and Br^- (aq) are in the ratio 5 : 6. Formation of Ag⁺(aq) is an endothermic process whereas formation of Br is an exothermic process. Enthalpy of formation of AgBr is - 110 kJ/ mol. The enthalpy of formation of Ag⁺ (aq) will be ______ kJ/mol.

Options

• 100

• 102

• 150

• 98

Answer 1

Enthalpy for the reaction \[\ce{Ag+ (aq) + Br- (aq) -> AgBr(s)}\] is : 90 kJ. Magnitude of enthalpy of formation of Ag⁺ (aq) and Br^- (aq) are in the ratio 5 : 6. Formation of Ag⁺(aq) is an endothermic process whereas formation of Br is an exothermic process. Enthalpy of formation of AgBr is - 110 kJ/ mol. The enthalpy of formation of Ag⁺ (aq) will be 100 kJ/mol.

Explanation:

\[\ce{Ag+ (aq) + Br- (aq) -> AgBr(s)}\]

ΔH = - 90 kJ

`(Delta"H"_("f" " Ag"^+ ("aq"))^0)/(Delta"H"_("f" " Br"^- ("aq"))^0) = 5/6 = (- 5)/6`    ...(i)

`Delta"H"_("f" " Ag Br")^0` = - 110 kJ mol^-1

- 90 = - 110 - `(Delta"H"_("f" " Ag"^+)^0 + Delta"H"_("f" " Br"^-)^0)`    ...(ii)

Solving (i) and (ii) we get

`Delta"H"_("f Ag"^+)^0` = 100 kJ mol^-1