General chem question

[Kami]

The activation energy for a reaction in the forward direction is 78 kJ. The activation energy for the same reaction in reverse is 300 kj. If the energy of the products is 25 kJ, then

a) what is the energy of the reactants.

I get -222 kJ

b) Is the forward reaction endothermic or exothermic and why?

c) Is the reverse reaction endothermic or exothermic and why?

d) What is the enthalpy change for the forward reaction and why?

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[Envision]

The activation energy for a reaction in the forward direction is 78 kJ. The activation energy for the same reaction in reverse is 300 kj. If the energy of the products is 25 kJ, then

a) what is the energy of the reactants.

I get -222 kJ

b) Is the forward reaction endothermic or exothermic and why?

c) Is the reverse reaction endothermic or exothermic and why?

d) What is the enthalpy change for the forward reaction and why?

Being that i just learned this (take a look at the tread titled gchem: enthalpy & eqlb) so i'l take a stab

a) I get 247KJ (equation given by DATstudent "energy of reactant + forward activation energy = energy of product + backward activation energy")
b) endothermic (postive dH)
c) endothermic (positive dH)

 

[dat_student]

a) I get 247KJ

b) endothermic (postive dH)

forward is exo (energy of reactant > energy of product)

c) endothermic (positive dH)

backward is endo (energy of reactant < energy of product)

...
d) What is the enthalpy change for the forward reaction and why?

-222

energy of reactant + change = energy of product

247 + change = 25

change = -222 (hence exothermic)

 

[Envision]

forward is exo (energy of reactant > energy of product)



backward is endo (energy of reactant < energy of product)

haha, thanx. what about part d?

 

[dat_student]

haha, thanx. what about part d?

see above (i just added it)

 

[Envision]

see above (i just added it)

i get it, that formula will give you +222 for the reverse rxn, which is logically correct. this helps a lot, thanx.