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I was under the impression that mass percent was an intensive property. Meaning that regardless of the sample size, the mass percent of an element of a compound would not change. If the mass percent of an element is 40% for a given compound, then it doesn't matter if you have 10g, 100g, or a 1000g of that compound. Therefore, for any given hydrocarbon, how do you go about increasing the mass percent?
The question asks: Which of the following is not associated with an increasing mass percent of carbon in a hydrocarbon?
I. An increase in the mass of carbon per gram of the compound.
- Ok, I understand that the more moles of carbon atoms you have in your compound, the higher the mass percent of carbon.
II. An increase in the mass of water formed upon oxidation of one gram of the compound.
- I understand that if you increase the amount of water formed, that must mean you have increased amounts of hydrogen present in your compound.
III. An increase in the mass of hydrogen per gram of the compound.
The answer says that if you increase the mass of water produced through the combustion process, then there is an increase in the mass of hydrogen atoms per gram of compound, increasing its mass percent. If hydrogen has a larger mass percent this would decrease the mass percent of carbon. Similar idea for the third response.
My question: If I have a simple hydrocarbon chain and I increase the mass of carbon per gram of hydrocarbon, then how does this increase the mass percent of carbon? The formula for mass percent of carbon is [(molar mass of carbon)(# moles of carbon)]/[molecular mass of the hydrocarbon]. The only two variables in this formula that can change are the # moles of carbon and the molecular mass of the hydrocarbon. If the number of moles increases (e.g., we extend our hydrocarbon chain from 6 carbons to 12 carbons), then won't that be reflected by the increase in molecular mass of the hydrocarbon? How do you increase the mass percent of carbon for the SAME hydrocarbon chain?
Furthermore, if you have a higher mass of hydrogen per gram of compound, don't you also need to increase the amount of carbons? How can you increase the number of hydrogens without increasing carbon for a hydrocarbon chain?
I am under the impression that for any given compound, the mass percent is always the same. That is, the mass percent of oxygen in C6H12O2 is some given constant percent.
Thanks for the help!
The question asks: Which of the following is not associated with an increasing mass percent of carbon in a hydrocarbon?
I. An increase in the mass of carbon per gram of the compound.
- Ok, I understand that the more moles of carbon atoms you have in your compound, the higher the mass percent of carbon.
II. An increase in the mass of water formed upon oxidation of one gram of the compound.
- I understand that if you increase the amount of water formed, that must mean you have increased amounts of hydrogen present in your compound.
III. An increase in the mass of hydrogen per gram of the compound.
The answer says that if you increase the mass of water produced through the combustion process, then there is an increase in the mass of hydrogen atoms per gram of compound, increasing its mass percent. If hydrogen has a larger mass percent this would decrease the mass percent of carbon. Similar idea for the third response.
My question: If I have a simple hydrocarbon chain and I increase the mass of carbon per gram of hydrocarbon, then how does this increase the mass percent of carbon? The formula for mass percent of carbon is [(molar mass of carbon)(# moles of carbon)]/[molecular mass of the hydrocarbon]. The only two variables in this formula that can change are the # moles of carbon and the molecular mass of the hydrocarbon. If the number of moles increases (e.g., we extend our hydrocarbon chain from 6 carbons to 12 carbons), then won't that be reflected by the increase in molecular mass of the hydrocarbon? How do you increase the mass percent of carbon for the SAME hydrocarbon chain?
Furthermore, if you have a higher mass of hydrogen per gram of compound, don't you also need to increase the amount of carbons? How can you increase the number of hydrogens without increasing carbon for a hydrocarbon chain?
I am under the impression that for any given compound, the mass percent is always the same. That is, the mass percent of oxygen in C6H12O2 is some given constant percent.
Thanks for the help!