A Little Help With Enthalpy/delta H

Nitroglycerine, C3H5(NO3)3 (l). Help with enthalpy?

We weren't given more info for the problem, but conditions and other info can either be extrapolated or assumed. To hold up my end of the deal, here's the correct standard enthalpy of formation of Nitroglycerine:

ΔH°rxn= [6*ΔH°f(N2(g)) + 10*ΔH°f(H20(g)) + 12*ΔH°f(CO2(g)) + 1*ΔH°f(O2(g))] - [4*ΔH°f(C3H5N3O9(L))]
Which works out to be :

-2.29E4 kJ = [6*0 kJ/mol + 10*-241.8 kJ/mol + 12*-393.5 kJ/mol + 1*0 kJ/mol] - [4*ΔH°f(C3H5N3O9(L))]

When solved for ΔH°f(C3H5N3O9(L)) using algebra you get +3.94E3 kJ/mol because energy has to be supplied for the rxn to occur.

However, I bagged a more important trophy today when I took the cute girl in chem for coffee, and we ended smoking some herb in her car to classical music and holding hands/kissing

Should I post stuff like this in the math and science forum, or does it matter? I'm sure some of you guys would like to see what our quizzes look like and we could learn from each other. Thanks for the help, guys. I look forward to discussing chem with you guys, as you guys have way more practical experience with chemistry than I could dream of.

Kneegrow Maw Maw

AP Chem Enthalpy Lab Help?

Calculate the enthalpy change, DeltaH, for each reaction in terms of kJ/mol for each reactant.
I had three reactions:

1. NaOH + HCL---->H20 +NaCl
2.NH4Cl +NaOH---->H20 +NH3 +NaCl
3. HCl +NH3---->NH4

The first reaction I measured out 50mL of 2.0M HCl into a foam cup, then I dumped in 50 mL of 2.0M NaOH solution into the cup...temperature change was 13.62 degrees C.

The second reaction I measured 50mL of 2.0M NaOH into a foam cup and then dumped 50mL of 2.0M NH4Cl solution. Temperature change = 1.77 C.

The third reaction I measured 50mL of 2.0M HCl into a foam cup and then dumped 50 mL of 2.0M NH3 solution. My temperature change was 13.45 C.

Can somebody help me and show me what to do possibly, I really have no clue. Thank you so much!

Hess's Law?? Calculate the reaction enthalpy/delta H?? Help!!!?

It is a little hard to explain step-by-step what to do so I hope you can follow what to do by looking at how I arranged the equations.

2 H2O(g) --------------------------> 2 H2O(l) -88
2 H2 + O2 ----------------------------> 2 H2O(g) -484
C + O2 ----------------------------> CO2 -393.5
CH4 -------------------------------> C + 2 H2 + 74.8
________________________________________...
CH4 + 2 O2 ---------------------> CO2 + 2 H2O -890.6 kJ

Once you cancel out the substances that appear BOTH on the left AND the right of the arrows you are left with your net equation.
Hope that helps.

College Chemistry help on Enthalpy and reactions?

H2(g) + O2(g) --> H2O2(g)
Heat of formation is -136.1 kJ/mol (I looked it up)

H2(g) + 1/2 O2(g) --> H2O(g)
Heat of formation is -241.8 kJ/mol (I looked it up)

Take the first equation and reverse it. It will change the sign of delta H.
Then double this equation. It will double the value of delta H.

2 H2O2(g) --> 2 H2(g) + 2 O2(g)
Heat of formation is +272.2 kJ/mol

Now take the second equation and double it. It will double the value of delta H.

2 H2(g) + O2(g) --> 2 H2O(g)
Heat of formation is -483.6 kJ/mol

Now add the two reactions together, and you will cancel out one mole of O2 and 2 moles of H2. Your reaction will now look more like the one you want. You add the two values of delta H together to get the delta H of the overall reaction. (+272.2) + (-483.6) = -211.4 kJ

The enthalpy for the decomposition of ONE MOLE would be half this value, or -105.7 kJ

A little help please?

hey i had this same EXACT problem to do... n my text book didn't have the delta H for C2H5Br... so afta hrs of searchin the net i got my answer...the delta H for C2H5Br... is 61.60... to find the delta H of the entire problem u have to do this: Product - Reactants... in this case it is -61.6 - [52.26+(-36.4)>> thats delta H for HBr]... this will equal -61.6-15.86= -77.46.... gud luck i hope this helped!

Vapor pressure, enthalpy of vaporization, and a little bit of math [slope] help?!?

The vapor pressure, P, of a certain liquid was measured at two temperatures, T.

Represented in a table:
T (in Kelvin) ------- P(in kPa)
[325] ------------------- [4.00]
[775] ------------------- [8.59]

What is the enthalpy of vaporization for this liquid? (Delta H vap) in kJ/mol?


If you were going to graphically determine the enthalpy of vaporization (delta H vap) for this liquid, what points would you plot?
x1 =
x2 =
y1 =
y2 =

Determine the rise, run, and slope of these points.

much help would be greatly appreciated! thank you