Science questions not covered in Chem 14A and 14B. Try to limit questions to chemistry (inorganic chemistry, physical chemistry, organic chemistry, biophysical chemistry, biochemistry, materials science, environmental chemistry).
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Some problems in the textbook give the names of the compounds but not the molecular formulas, for instance: "..a vigorous reaction takes place, and elemental molten barium and solid aluminum oxide are formed." Are we expected to know the formulas for compounds like aluminum oxide? or just common polyatomic ions?
Formulas will typically be given on the test if they have never been mentioned before, and for simpler compounds, you should be able to figure them out. It is definitely useful to have the common polyatomic ions memorized.
You should be able to write out the molecular formulas of common compounds like aluminum oxide or sodium chloride using the number of valence electrons each atom has. In an ionic compound, you can figure out how many valence electrons each element needs to fill their valence electron shell and balance the charges of each element to find the molecular formula. Having the polyatomic ions memorized will help you with writing some of the molecular formulas that contain them because you will have the charges of each one memorized.
You'll need to know combustion reaction reactants and products. Other than that, our TA mentioned that any other molecular formulas that may be more complex are usually given to you on the test. That being said, it might be a good idea to eventually memorize polyatomic ions and understand how to form molecular formulas.
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