Any Chemistry Majors on TUG? Help needed...

[johnsontrio]

I know the folks on TUG are a smart bunch so I offered to post this as a last resort. DD is a college freshman in the Nursing program. Her Chem teacher has issued an assignment worth 100 points, about 10% of the total grade. It is a problem not related to what they are actually studying. So far, she and classmates have gone into the professor's office hours, asked the chem major in the learning center and sent it to 2 different high school chem teachers without any luck. She also consulted my BIL who has a water science degree and treats chemical wastes from refineries. Can anyone make heads or tails of this? I would be grateful even to be pointed in the right direction regarding finding the solution.

1. You have been asked to produce 7.8 grams isotopically labeled copper sulfate pentahydrate. You start with copper metal that contains 95% (w/w) 67 (superscript) Cu, which has a half life of 61.83 hours and 83% (w/v)
sulfuric acid. Calculate the charges of the reactants, if the isolated yield reported in the literature was 91.3% of
theory. What is the copper metal contaminated with?

2. What is the weight of 67(superscript) Cu in your product, if synthesis and purification took 2 days?

3. In the second step, you heat all of your product to 650 C, where copper(II)sulfate decomposes to copper(II)oxide and sulfur trioxide. How many liters of sulfur trioxide do you release under standard conditions.
Assuming the latter reaction has an equilibrium constant of 2.4 times 10 to the 8th power, what is the expected yield of copper(II)oxide if this step took 16 hours?

Any help appreciated!

 

[normab]

This is part of an exam? I can give you an overview of how to proceed...

This type of question is based on first writing out the chemical reaction and balancing it. From that the contaminant will be obvious.

Then you use the amounts given (adjusting for low yield) and molar ratios, molecular weights to calulate the amounts of the reactants.

For the second question you would use the starting amount of Cu (alone, another ratio) and half life to calculate the amount left after 2 days.

The third question is asking you write another equation.

Then use the ideal gas law to perform the first calculation and use the equilibrium constant to calculate the concentration of the product, adjusting again for decomposition due to the half life.

I think a Chemistry 101 book would be helpful in solving all of these problems. They typically have lots of examples. (at least they did in the 1970s when I studied...)

Good luck to your daughter!

Norma

 

[Barbeque]

My son is in AP courses in high school. He has previously taken Chemistry and Physics. His teachers suggested going on the internet and using http://www.khanacademy.org/ to help with problems.
Khan Academy also has a lot of videos on youtube.
Our son says this really helped him.

 

[johnsontrio]

This isn't an exam but is a take home assignment. Thanks to you both for helping us get a least a starting point for tackling this problem. There is a bit of a language barrier with the professor. He's German, but it seems as though he is "speaking Greek" on this one. DD should be able to use this info to get help from the students in the Learning Resource Center.

 

[T_R_Oglodyte]

Personally, I think this is an excellent assignment for students, worth about 10% of the grade. It involves two steps. First you have to understand what the problem is asking, which in this case involves taking concepts and ideas they have been exposed to in class, dressing them in different clothes and putting them into a new context, and seeing if they can figure it out. It's a good example of how certain basic concepts come back again and again; the key is recognizing them.

After that, the problem involves collecting and working with information that they probably haven't worked with previously, and integrating that information in a new way. A good challenge for students who are ready to expand.

In my youth, I had many teachers who handed out problems like this, and the ability to solve problems like this was the difference between an A and a B in class. B meant you had mastered the material in the class. A meant you had mastered the material and demonstrated that you could carry the material beyond the material that had been taught in the class.

 

[normab]

First you have to understand what the problem is asking, which in this case involves taking concepts and ideas they have been exposed to in class, dressing them in different clothes and putting them into a new context, and seeing if they can figure it out. It's a good example of how certain basic concepts come back again and again; the key is recognizing them.

You say it well, that is the hardest part, figuring out how this problem fits into all the concepts they have learned. And I agree with you that it separates the As from the Bs!

I must confess I loved multiple step problems like this, Chemistry nerd that I am!!!

 

[johnsontrio]

Steve and Norma~ I certainly agree with you both in theory and am happy to see that DD is getting the education that we are paying for. Unfortunately the nursing program is very rigorous and her anatomy course is demanding most of her time. I understand that this type of assignment would come at the end of the semester so that the students can pull together everything they have learned and try to apply it. Luckily she is heading into the final with a strong A and her work on this assignment may bring her grade to a B. It's a bummer that she needs to be studying for finals right now and can't spend more time on it. She is carrying 19 credits and plays a sport. We are happy that her course load drops to 17 credits in the Winter semester. The nursing program is year round for 4 years.

On the bright side, this bodes well for us baby boomers. My DH and I are both nurses and neither of us were challenged in the way DD is being challenged in her first year of the program. DH took an anatomy course as a prerequisite for his Master's Anesthesia program. DD is using the same book he did as a post graduate nurse and is actually learning it in more detail. If DD's program is representative of what is going on in colleges these days, we should all be provided with quality medical care as we age.

 

[Kal]

Personally, I think this is an excellent assignment for students, worth about 10% of the grade. It involves two steps. First you have to understand what the problem is asking, which in this case involves taking concepts and ideas they have been exposed to in class, dressing them in different clothes and putting them into a new context, and seeing if they can figure it out. It's a good example of how certain basic concepts come back again and again; the key is recognizing them...

Steve - This is an interesting assignment that would have kept me up late into the night until I was able to get a solution. Thinking back to my days as a chemical and chemical engineering upstart, it is typical of many assignments but is really out of the mainstream in today's electronic based approach to solution. Today we first reach for Google or other software to plug in parameters and turn the crank. A fairly mindless approach where today's students thrive on keywords and shortcuts rather than hard learned basics. This problem is a throwback demanding a pure knowledge of chemistry, stoichiometry and quantitative analysis which speaks well of the instructor.

But for me, it gives me a headache just thinking about having to go thru what it will take to get the answer!

 

[Elan]

Many of the classes I took in getting my degree were required for learning problem solving, and not really intended for learning the specific material at hand. For instance, as an electrical engineering student, I had to take Statics, Dynamics, Strength of Materials, Thermodynamics, etc. (along with the requisite chemistry, physics and math). In my job I use none of that education, except for the inherent analytical problem solving skills, which I use daily.

normab effectively "solved" the problem in her first post, as she outlined the analytical steps req'd to find the numerical solutions. That's 90% of the exercise, IMO. Getting the correct numerical solutions is the other 10%.

 

[Patri]

You lost me at sulfate pentahydrate.

 

[Kal]

You lost me at sulfate pentahydrate.

Oh, the common name is di-methyl chickenwire.

 

[T_R_Oglodyte]

Oh, the common name is di-methyl chickenwire.

This is inorganic. It's more like sodium baloneyate.