Question

CONTINUE>>>>>>>>>>>

The enthalpy changes for two different hydrogenation reactions of C2H2 are:

C2H2+H2---->C2H4 Delta H 1 (there is a degree sign....standard enthalpy of formation??)

*****WAIT A SECOND, IF I USE THE HEAT OF FORMATION VALUES TO CALCULATE THEN WOULD THAT GIVE THE ENTHALPY OF RXN???...which is not relevant to this question,right???
*****But if you change the sign to a neg then how do you know that it is positive originally???I AM VERY VERY PERPLEXED,DR.BOB!!!!!!!!!

I DO UNDERSTAND THAT YOU HAVE TO SWITCH ACCORDING TO HESS'S Law, but I DO NOT UNDERSTAND HOW YOU KNOW THE SIGNS......!!!!!!!!!!!!!!!!!!!!
Why is it pos to neg ??????????
I thought it is the other way around!!!!

BUT DO YOU UNDERSTAND WHAT I DO NOT GET??? IF NOT, I WILL TRY TO CLARIFY IT.


THANK YOU FOR YOUR PATIENCE!!!!

C2H2+2H2---->C2H6 Delta H 2 (there is a degree symbol)



Which expression represents the enthalpy change for the reaction below?

C2H4+H2---->C2H6 Delta H = ?

Answer 1

See your post above.