Chapter 7 is all about converting grams to moles and back again. You will also know how to convert moles to atoms or moles to molecules (and backwards, of course).
One thing you can't do is convert directly from atoms to grams or molecules to grams. You have to convert to moles first. (Same thing if you're converting in the opposite direction.)
You also need to know how to calculate (and use) percent by mass of an element in a compound.
For example, what is the percentage by mass of carbon in carbonic acid?
Finally, you need to know how to convert percent by mass (or experimental composition data) to empirical formulas and molecular formulas (if you have the molar mass).
For example, if a compound contains 11.2% hydrogen and the remainder is oxygen, then what is the empirical formula of the compound?
Furthermore, if the molar mass of this compound is 18.0 grams per mole, then what is the molecular formula of this compound?
What is a mole?
What is the definition of mass percent?
What is the conversion factor you can get from a mass percent?
For example, if you know that water is 88.8% oxygen, how many grams of oxygen are present in 6.90 grams of water?How do you calculate a molecular formula if you know the molar mass and the empirical formula?
For example, if the empirical formula is CH2 and the molar mass is 42.0 grams per mole, then what is the molecular formula?
(Note: If you're given masses instead of percents for the elements, you can just start with the masses that you're given, and don't need to assume 100 grams.)
Homework Chapter 7
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Return to the Schedule.
Go back to the study guide for Chapter 6
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