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AP Chemistry716 views·Updated Jul 16, 2026Introduction to Elemental Composition
Practice fundamental concepts of mass percentage and the law of definite proportions to determine the relative mass of elements in a pure substance.
A student analyzes two different samples of a pure liquid compound containing only carbon and oxygen. Sample 1 contains 12.0 g of carbon and 16.0 g of oxygen. Sample 2 contains 24.0 g of carbon and 32.0 g of oxygen. Which of the following laws best explains why both samples have the same mass percentage of carbon?
- A student analyzes two different samples of a pure liquid compound containing only carbon and oxygen. Sample 1 contains 12.0 g of carbon and 16.0 g of oxygen. Sample 2 contains 24.0 g of carbon and 32.0 g of oxygen. Which of the following laws best explains why both samples have the same mass percentage of carbon? — The law of definite proportions
- A 50.0 g sample of an unknown compound contains 20.0 g of calcium, 6.0 g of carbon, and 24.0 g of oxygen. What is the mass percentage of calcium in this compound? — 40%
- A pure sample of a hydrocarbon is 80.0% carbon by mass. If a student analyzes a 25.0 g sample of the same hydrocarbon, what is the mass of hydrogen present in the sample? — 5.0 g
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Practice converting between mass, moles, and number of particles using Avogadro's constant and the fundamental concept of the mole.
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Analyze the economic, religious, and political factors that drove European powers to the Americas during the 15th and 16th centuries.
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Students love us — and so will you.
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.