Chemistry
posted by Kathryn .
I am beyond desperate. I do not understand how to calculate heat change at all and I have been looking online and reading my book for the last three hours. Below is posted a problem. It would be amazing if someone could work through it and explain each step they are doing and why they are doing it.
Calculate the heat change for the formation of lead(IV) chloride by the reaction of lead(II) chloride with chlorine
PbCl2(s) + Cl2(g) > PbCl4(l) H=?
___
Use the following thermochemical equations:
Pb(s) + 2Cl2(g) > PbCl4(l) h= 329.2kj
Pb(s) + Cl2(g) > PbCl2(s) h= 359.4kj

I flipped the second equation around to go with Hess's law which gives me a h value of 359.4 for the second one but I am lost after that.

ask your teacher.

I think you're trying to make it too hard.
Use equation 1 as is, reverse equation 2 (and change the sign of delta H for equation 2), add 1 to 2 and add delta H1 to the new delta H 2.
Pb(s) + 2Cl2(g) ==> PbCl4(l)
PbCl2(s) ==>Pb(s) + Cl2(g)

Pb(s)+2Cl2(g)+PbCl2(s)==>PbCl4(l)+Pb(s)+Cl2(g)
Note that Pb(s) cancels.
Note that 2Cl2 on the left and 1 Cl2 on the right leaves 1 Cl2 on the left to leave you with
Pb(s) + Cl2(g) ==>PbCl4(l)
329.2 + 359.4 = ?? 
to Drbob222 you actually are left with PbCl2(s) + Cl2(g) ==> PbCl4 because theres 2Cl2 on the first equation and the reverse equation only cancels out one of those Cl2's
Respond to this Question
Similar Questions

Physical science
In my tenthgradelevel physical science class, we're studying heat, and I completely don't get it. I'll read the definition for specific heat over and over, and I still don't understand it. "For all substances, specific heat is a … 
English
I've been reading the book but am having major trouble getting through it because of the way it is written. I need to know three major events in the book but cannot pinpoint them because I just don't understand the dialect. 
chemistry
Posted a question earlier but it was the wrong question. If anyone could help it would great if you could explain this would help also. Thanks ^ = subscript Calculate ke for(equlibrium concentration below problem 2CO^2(g) + heat 2CO(g) … 
Math
I posted this problem the other day and someone answered it but when I checked my book I realized that I wrote the problem wrong. This morning when I posted I had put the wrong answer. The answer is suppose to be 1/8 but I don't understand … 
English
Posted by rfvv on Tuesday, August 31, 2010 at 8:19pm. 1. There is a girl who is reading a book with legs crossed on the sofa. 2. There is a girl reading a book with her knees folded and raised on the sofa. 3. There are a dog and a … 
Critical Reading
Can someone please help me with this question? 
English
Please help me find these words in the book hatchet. These words are located in chapter 1316 and all I need to knnow is where these words are located. I have found the book online and I have posted it underneath. I have done a couple … 
Foreign languages
Can you please check these sentences, Writeacher? 
Statistics
Given the following information, determine the 68.3 percent, 95.5 percent, and 99.7 percent confidence intervals. overbar above X equals 4.33 comma SE sub m equals 3 I've looked at the table as recommended. I just do not understand … 
Math
Hey! So, I've been working on this problem for awhile but I'm currently a bit dumbfounded on how to solve it. I think this question has been answered before but I still don't quite understand how it works or how to explain it. The …