Thursday, March 25, 2010

Chemistry tutor please

I am really, really loving my Chemistry class. I just started it last Friday(3/19/2010) and I'm already on Chapter 6. It is chalk full of math and equations and story problems--you know how much I love those! Just four more lessons and I'm at the midterm!

I am amazed at how much information I have retained from high school Chemistry. Especially amazing when you consider that I got a C- in H.S. Chem! Amazing, that is until yesterday, when I got stuck. I am totally and completely stumped on how to solve two types of problems. I have read and re read the book. I have used all the Independent Study online resources. I have tried every math page and google page I could find trying to find out how to work these questions, all to no avail. Today I think I will go and beg some help off some of Dave's coworkers at the high school, perhaps they will take pity on me.

In case they can't help perhaps one of you can. Are any of you Chemistry majors or Chemistry whizzes or even just passed Chemistry with a C- or better? Maybe you can help me. These are the two stumpers and I just need to know how to set up the problem.

1.-- A 500.0-g iron bar at 212 degrees C is placed in 2.0 L of water at 24.0 degrees C. What will be the change in temperature of the water?(Assume no heat is lost to the surroundings.)

The equation: (mass of substance)*(specific heat of substance)*(change in temp)=heat. The specific heat of iron is .473J/gC and the specific heat of water is of course 4.184J/gC.

The answer is 5 degrees. But I have tried this problem 4 different ways and have gotten 4 degrees and 6 degrees but never 5 degrees. There was a problem just like it on the lesson quiz and I got it wrong. I'm sure there will be another one on the midterm.
2-- The actual mass of one atom of an unknown isotope is 2.18x10(-22)g. Calculate the atomic mass of this isotope. I HAVE NO IDEA. I think my brain is fried over the other problem and I'm having difficulty getting past it. I'll reread the chapter again right now to see if I missed how to work this calculation.

Dave says I'm probably just overthinking it and that they are likely easy solutions but he couldn't figure them out either.

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