Find the Delta H for the overall reaction below, given the following minor react

Question

Find the Delta H for the overall reaction below, given the following minor reactions and their Delta H values (remember, the minor reaction molecules to total whats left in the major/overall reaction): overall reaction:N_2H_4(l)+ H_2(g) rightarrow 2NH_3(g) minor reactions (3 of them): N_2H_4 (l) + CH_4 O(l) rightarrow CH_2O(g) + N_2 (g) + 3H_2 (g) Delta H = -37 kJ N_2 (g) + 3H_2 (g) rightarrow 2NH_3(g) Delta H = -46 kJ CH_4 O(l) rightarrow CH_2 O(g) + H_2 (g) Delta H = - 65 kJ + 35 kJ +2 kJ -68 kJ -18 kJ -2 kJ

Explanation / Answer

Ans. N2H4(l) + CH4O(l) ----> CH2O(g) + N2(g) + 3H2(g) ; Reaction 1 , dH = -37 kJ

N2(g) + 3H2(g) ----> 2NH3(g)                                             Reaction 2; dH = -46 kJ      

CH4O(l) ----> CH2O(g) + H2(g)                                           Reaction 3; dH = -65 kJ

N2H4(l) + H2(g) ----> 2NH3(g)                                             Reaction 4; dH = ?

Using Hess’s Law, reaction 4 can be written as the sum of-

N2H4(l) + CH4O(l) ----> CH2O(g) + N2(g) + 3H2(g)          ; dH = -37 kJ

N2(g) + 3H2(g)      ----> 2NH3(g)                                        ; dH = -46 kJ

CH2O(g) + H2(g)   ----> CH4O(l)                                         ; dH = +65 kJ (Revrs. of Rxn 3)

N2H4(l) + H2(g)     ----> 2NH3(g)                                        Reaction 4; dH = ?

Now,

            dH (Rxn 4) = (-37 kJ) + (-46 kJ) + 65 kJ = - 18 kJ

So, correct option is- D.

Related Questions

Navigate

• Browse (All)
• Browse F
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.