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Phosgene is COCl2, and cobalt chloride is CoCl2.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Phosgene is COCl2, and cobalt chloride is CoCl2. Write what re.findall(r"([A-Z][a-z]?)(\d*)", f) gives for each. Then find the molar mass of phosgene. Use C , O and Cl . What happens if you ask for the molar mass of CoCl2 and cobalt is not in the dictionary?
Need a reminder? The key ideaShow
Molar mass the sum of atomic mass times count for every element. In Python: sum(atomic[el] * n for el, n in counts.items()). A formula is read into symbols and counts with re.findall(r"([A-Z][a-z]?)(\d*)", formula), after brackets are opened. Mass percent .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Phosgene. [('C', ''), ('O', ''), ('Cl', '2')]: carbon, oxygen and two chlorine.
Step 2. Cobalt chloride. [('Co', ''), ('Cl', '2')]: the small o belongs to the symbol Co.
Step 3. Molar mass of phosgene. g/mol.
Step 4. Cobalt missing. atomic['Co'] stops the program with KeyError: 'Co'. Add cobalt to the dictionary first.
Answer: g/mol for phosgene; the case of the letters decides the elements.
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