Question

Suppose that 0.610mol of methane, CH4 (g), is reacted with 0.760mol of fluorine, F2 (g) , forming CF4 (g) and HF (g) as sole products. Assuming that the reactionoccurs at constant pressure, how much heat is released?

Answer 1

CH₄ (g) + 4F₂ (g)   ------> CF₄ (g) + 4HF (g)    + ?H = ?

?H = Bond energies of product- bond energies of reactant

      = [ (-679.9 KJ) + ( 4 x -268.61) ] - [ (-74.8 KJ ) + ( 4x 0KJ ) ]

      = -1679.54KJ

So from the equation ,

1 mole of CH₄  reacts with 4 moles of F₂

Y mole of CH₄  reacts with  0.76 moles of F₂

Y = ( 1 x 0.76 ) / 4

   = 0.19 moles

So 0.610 - 0.19 = 0.42 moles of CH₄ left unreacted

4 moles of F₂ upon reaction produces 1679.54 KJ of energy

0.76 moles of F₂ upon reaction produces (1679.54x 0.76) / 4 ]KJ

                                                                = 319.1 kJ