Chemistry (including Biochemistry)/Metal content in salt

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Expert: - 11/10/2011


Question
I'm trying to find out how to properly calculate how much metal I'm putting into solution. From what I've read copper sulfate pentahydate has 25% metal. Can you tell me how to easily calculate this so I can figure others like bismuth nitrate, cobalt sulfate, etc.

I'm assuming if I put 100 grams of copper sulfate crystals into 1 liter of water I will have 25 grams of metal in that one liter of solution.   Which would be 25 g/l copper metal.

Answer
Hello Chris!

You need to review the concept of a mole as a unit in chemistry. It is defined as a specific number of molecules, 6.02 x 10^23 to be precise.
http://en.wikipedia.org/wiki/Mole_(unit)
http://en.wikipedia.org/wiki/Molar_mass
http://en.wikipedia.org/wiki/Molar_solution
http://en.wikipedia.org/wiki/Chemical_equation

The chemical formula of your salt should tell you how many metal ions are present in one mole of the solution. It will be different for each metal ion. If you have access to the jar of salt it will tell you the chemical formula. Else you will need to reference a periodic table to make sure the salt has balanced charges. Aluminum can have a charge of +3, so it would need three chlorides at -1 to balance it. Solid salts like to be balanced in this way.

So let's work through your example.

Your chemical is CuSO4*5H2O, if it is copper II sulfate. (It will be different if it is copper III; that has a charge of +3. These things matter. Check.) You should be able to derive the molar mass by looking it up online or looking at a periodic table. (mass of Cu+mass of S+mass of O+mass of H. Note that there are more than one oxygen atom in the molecule, and we're concerned with the mass of the whole thing. You will need to figure out how many O's in total and then multiply that by oxygen's molar mass, and add that to all the other masses to get the molar mass of the compound.)

Now you can calculate *the number of moles of copper sulfate pentahydrate* in 100g.

Then, you can take that number and assume that there is one copper atom per mole of copper sulfate by looking at the formula. If there were two copper atoms per molecule, you would need to multiply by the molar ratio of two copper atoms per one molecule in your calculation. But in this case we are lucky: it is one to one.

Then you can take that number of copper atoms - equal to the number of copper sulfate pentahydrate molecules  - and multiply it by the molar mass of copper (taken from the periodic table). This will tell you the total number of grams of copper in your solution.

So,

100 g copper sulfate pentahydrate * [(1 mole copper sulfate pentahydrate)/(molar mass copper sulfate pentahydrate in grams)] * [(1 mole copper)/(1 mole copper sulfate pentahydrate)] * [(grams of copper)/(1 mole of copper)] = grams of copper in solution

You should write this out on paper to see that the units cancel, leaving you with grams of copper at the end.

If you want the percent copper in the solution by mass, water has a density of one gram per mililiter. So a liter of water weighs a thousand grams. You can divide your copper mass by the mass of water+copper sulfate pentahydrate to get an idea of what percentage of copper there is in solution by mass.

However, chemists prefer giving amounts of atoms in solution by referring to them as 'molar' solutions. 1 M solution has one mole of stuff per liter of solution. These numbers are often easier to handle, especially since chemical reactions happen at molar ratios of things rather than percentages of ions in solution.

Good luck and stick with chemistry!

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Trista Robichaud, PhD

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No homework questions, especially ones copied and pasted from textbooks. I will answer questions about principles or give hints, but I do not do other's homework. I'm comfortable answering basic biochemistry, chemistry, and biology questions up to and including an undergraduate level of understanding. This includes molecular biology, protein purification, and genetics. My training/inclination is primarily in structural biology, or how the shapes of things affect their function. Other interests include protein design, protein engineering, enzyme kinetics, and metabolic diseases such as cancer, atherosclerosis, and diabetes. My chemistry weaknesses are that I do not know organic or inorganic synthesis well, nor am I familiar with advanced inorganic reactions. I will attempt quantum mechanics and thermodynamics questions, but primarily as they relate to biological systems. Furthermore, I cannot tell you if a skin photograph is cancerous, or otherwise diagnose any disease. I can tell you how we currently understand the basic science behind a disease state, but I cannot recommend treatment in any way. Please direct such questions to your medical professional.

Experience

I hold a PhD in Biomedical Science from the University of Massachusetts Medical School in Worcester. I specialize in Biochemistry, with a focus on protein chemistry. My thesis work involved the structure and functions of the human glucose transporter 1. (hGLUT1) Currently I am a postdoc working in peptide (mini-protein) design and enzymology at the University of Texas Health Science Center in San Antonio, Texas. I am in Bjorn Steffensen's lab (PhD, DDS), studying gelatinase A and oral carcinoma.

Organizations
2001 American Association for the Advancement of Science
2007 American Chemical Society
2007 Protein Society
2011 UTHSCSA Women’s Faculty Association


Publications
Levine KB, Robichaud TK, Hamill S, Sultzman LA, Carruthers A. Properties of the human erythrocyte glucose transport protein are determined by cellular context. Biochemistry 44(15):5606-16, 2005. (PMID 15823019)
Robichaud TK, Appleyard AN, Herbert RB, Henderson PJ, Carruthers A “Determinants of ligand binding affinity and cooperativity at the GLUT1 endofacial site” Biochemistry 50(15):3137-48, 2011. (PMID 21384913)
Xu X, Mikhailova M, Chen Z, Pal S, Robichaud TK, Lafer EM, Baber S, Steffensen B. “Peptide from the C-terminal domain of tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) inhibits membrane activation of matrix metalloproteinase-2 (MMP-2)” Matrix Biol. 2011 Sep;30(7-8):404-12. (PMID: 21839835)
Robichaud TK, Steffensen B, Fields GB. Exosite interactions impact matrix metalloproteinase collagen specificities. J Biol Chem. 2011 Oct 28;286(43):37535-42 (PMID: 21896477)

Poster Abstracts:
Robichaud TK, Carruthers. A "Mutagenesis of the Human type 1 glucose transporter exit site: A functional study." ACS 234th Meeting, Boston MA. Division of Biological Chemistry, 2007
Robichaud TK, Bhowmick M, Tokmina-Roszyk D, Fields GB “Synthesis and Analysis of MT1-MMP Peptide Inhibitors” Biological Chemistry Division of the Protein Society Meeting, San Diego CA 2010
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Catalytic Domain Exosites Contribute to Determining Matrix Metalloproteinase Triple Helical Collagen Specificities” Dental Science Symposium. UTHSCSA 2011
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon Research Conference on Matrix Metalloproteinase Biology, Bristol RI 2011


Education/Credentials
Oakland University, Auburn Hills MI BS, Biochemistry 1998
University of Massachusetts Medical School, Worcester MA PhD, Biochemistry & Molecular Pharmacology 2001-2008
University of Texas Health Science Center, San Antonio TX Postdoc, Biochemistry 2009-Present


Awards and Honors
1998 Honors College Graduate, Oakland University
2009 Institutional National Research Service Award, Pathobiology of Occlusive Vascular Disease T32 HL07446
2011 1st Place, Best Postdoctoral Poster, Dental Science Symposium, UTHSCSA, April 2011


Past/Present Clients
Invited Seminars:
Robichaud TK, Fields GB. “Synthesis and Analysis of MTI-MMP Triple Helical Peptide Inhibitors” Pathology Research Conference, University of Texas Health Science Center San Antonio Pathology Department (June 18th, 2010)
Robichaud TK & Hill, B “How To Give A Great Scientific Talk” Invited Lecture, Pathobiology of Occlusive Vascular Disease Seminars, UTHSCSA (Nov 11th 2010), Cardiology Seminar Series, Texas Research Park (Feb 21st, 2011)
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon-Keenan Research Seminar “Everything You Wanted to Know About Matrix Metalloproteinases But Were Afraid to Ask” Bristol, RI (Aug 6th, 2011)

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