Calculate the enthalpy of the reaction
4b(s)+3o2(g)→2b2o3(s)
given the following pertinent information:
b2o3(s)+3h2o(g)→3o2(g)+b2h6(g), δh∘a=+2035 kj
2b(s)+3h2(g)→b2h6(g), δh∘b=+36 kj
h2(g)+12o2(g)→h2o(l), δh∘c=−285 kj
h2o(l)→h2o(g), δh∘d=+44 kj

Answer : The enthalpy of the reaction is, -2552 kJ/mole

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The given enthalpy of reaction is,

The intermediate balanced chemical reactions are:

(1)    

(2)    

(3)    

(4)    

Now we have to revere the reactions 1 and multiple by 2, revere the reactions 3, 4 and multiple by 2 and multiply the reaction 2 by 2 and then adding all the equations, we get :

(when we are reversing the reaction then the sign of the enthalpy change will be change.)

The expression for enthalpy of the reaction will be,

Therefore, the enthalpy of the reaction is, -2552 kJ/mole

your answer would be “dry”

it is the most commonly accepted one