CHEMISTRY

posted by .

Post a New Question Current Questions
Homework Help: Chemistry
Posted by Anonymous on Thursday, November 14, 2013 at 8:45pm.


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 = ?

Ignore the things below.....

First Name:
School Subject:
Answer:

Related Questions

Geometry - Given circle A with circumference 20 pi and the length of arc KD ...
Logic - Can someone please help me solve these problems? I have to use the 17 ...
Economics - I am on the chapter for International Trade in the book. I neew to ...
Sabian - If air resistance offered to the motion of a projectile by the ...
Pre-Cal. - Describe the end behavior of f(x)=2x^4-5x+1: A. x-->‡, f(x)-->...
Economics - I have the following question in my assignment: The cost of ...
Philosophy (Logic) - I need help constructing a formal proof of validity for the...
math - Solve this : (8x^3 ) - (168x^2) + ( 864x) = 1120 please >>>>&...
Math - help please anyone? i'm having a hard time solvig these problems LOGIC ...
chemistry - Given the equilibrium constant values: N2 + 1/2O2 >>> N2O...

  • CHEMISTRY -

    No, I'm still not in touch with you I don't think. Are you supposed to calculate dH1 and dH2 or are those given to you. I assume they have not been given and you must calculate them. If so then dHf certainly is relevant to the question. If you do dHrxn = (n*dHf products) - (n*dH reactants) you get dHrxn1. Then you do the same for the second reaction and that gives you dHrxn2. Then you combine the reverse of H1 rxn (and you reverse the sign whatever it happens to be)(see note below) and add it to the forward reaction for H2 (and keep the sign whatever it happens to be). That will give you the reaction you are looking for as well (add the reverse of rxn 1 and the forward rxn of 2 and see if that doesn't give you the reaction you want at the end). Then you add the NEW values with the NEW signs to give the dH for the NEW reaction. Any sign that is negative is exothermic for that reaction and any sign that is positive is endothermic for that reaction.
    NOTE. Note that saying "reverse the sign" is the same as saying "change the sign to the negative" or "take the negative of that value" or any number of similar statements. I don't think I ever said anything about "changing the sign to a negative" but if I did I shouldn't have. In thermochemisty all kinds of equations are written and tabulated with delta H values. If the value is positive the reaction is endothermic and if negative the reaction is exothermic. If we don't like the equation as it is but we want the reverse of that equation, we simply reverse the equation and reverse the sign (a + sign becomes a - sign or a - sign becomes a + sign). Does that change whether it is exothermic or endothermic. You bet it does. If
    A==> B is dH = -15 kJ then
    B==> A is dH = +15 kJ and what was an exothermic reaction (-15 kJ) becomes an endothermic reaction (+15 kJ). I hope this helps but if not I don't mind trying again. If you pursue this further, please write the question first and comments later. Also, please avoid using all caps--that makes it difficult to read

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    1)Which thermochemical equation and data does not agree with the other two written?
  2. chemistry

    Calculate the value of DHo for the reaction 2 CH4 (g) -> C2H6 (g) + H2 (g) given the following thermochemical equations: C2H2 (g) + H2 (g) -> C2H4 (g) delta = – 175.1 kJ C2H6 (g) -> C2H4 (g) + H2 (g) Delta = + 136.4 kJ C2H2 …
  3. To whoever "Anonymous" is

    You posted this: Posted by Anonymous on Thursday, July 25, 2013 at 10:16am. Provide a brief overview of government policy toward Native American’s during the period of 1850 to 1900 and the impact this policy had on their lives. You …
  4. Chemistry

    Please explain. The enthalpy changes for two different hydrogenation reactions of C2H2 are: C2H2+H2---->C2H4 Delta H 1 C2H2+2H2---->C2H6 Delta H 2 Which expression represents the enthalpy change for the reaction below?
  5. CHEMISTRY

    Please explain. The enthalpy changes for two different hydrogenation reactions of C2H2 are: C2H2+H2---->C2H4 Delta H 1 C2H2+2H2---->C2H6 Delta H 2 Which expression represents the enthalpy change for the reaction below?
  6. CHEMISTRY

    I know I posted this question before, but can you clarify it?
  7. Chemistry

    I know I posted this question before, but can you clarify it?
  8. Chemistry

    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?
  9. Chemistry

    Please also, help me set up this problem. Acetylene, C2H2, can be converted to ethane, C2H6, by a process known as hydrogenation. The reaction is C2H2(g)+2H2(g)⇌C2H6(g). Given the following data at standard conditions (all pressures …
  10. Chemistry

    Oxyacetylene torches are fueled by the combustion of acetylene, C2H2. 2C2H2(g) + 5O2(g) --> 4 CO2(g) + 2H2O(g) If the enthalpy change for the reaction is -2511.14 kJ/molrxn, how much heat can be produced by the reaction of a. 2mol …

More Similar Questions