# Given the following data, what is the enthalpy associated with the given equation? ##

##
Given...

#2H_2(g) + O_2(g) rarr 2H_2O(g)# #;DeltaH_1^@=-484*kJ*mol^-1# #(i)#

#2CO(g) + O_2(g) rarr 2CO_2(g)# #;DeltaH_2^@=-566*kJ*mol^-1# #(ii)#

...what is the enthalpy associated with the reaction...?

#H_2(g) + CO_2(g) rarr CO(g) + H_2O(g)# ?

Given...

...what is the enthalpy associated with the reaction...?

##### 2 Answers

We treat the individual equations as simultaneous linear equations....

and get an endothermic reaction..........

#### Explanation:

We have:

We want

If I add

But this is EQUAL to

And thus

This is the Hess's law

In the Hess's law you should add both the reactions like this

For example

Hess's law states that the addition of total heat absorbed and and released of some reactions is equal to

And you should know that the energy absorbed or released is expressed as

For an equation like

A + B=AB

C+B= CB

A + B = AB

C+ B= CB

Cancel the same reactants on both sides and add the reaction

A + C = CB + AB

Even though its not possible

So if we add the the

Even you can get the

For example if the

C + B = CB

CB = C +B

And consider

A + B

Now again do what we did before

A + B = AB

CB = C + B

CB + A = C + AB

And now add the

Do the same for this reaction

If we cancel the same terms on both side that is

And that's not a sensible reaction and what we wanted

so we do what we did in the above example

Add both the reactions

Cancel the same terms

Now add the

But this is the

not

To caculate the

= 41kJ/mol