M.13 Polychlorinated biphenyls (PCBs) were once widely used industrial chemicals but were found to pose a risk to health and the environment. PCBs contain only carbon, hydrogen, and chlorine. Aroclor 1254 is the trade name for a PCB with molar mass 360.88 g⋅mol−1. Combustion of 1.52 g of Aroclor 1254 produced 2.224 g of CO2,and combustion of 2.53 g produced 0.2530 g of H2O. How many chlorine atoms does an Aroclor 1254 molecule contain?
I don’t really get how to start on this problem I don’t get how you would determine the amount of chlorine atoms.
M.13
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Re: M.13
Postby Ayaan_Ekram_2J » Thu Oct 21, 2021 11:06 pm
Hello!
To start this problem, we must first convert the grams of CO2 and H2O given to moles by dividing by the molar masses. Then, we can convert the moles of CO2 to moles of C as 1 mole of CO2 contains 1 mole of C. We do the same with water, but instead use the fact that there are 2 moles of H for every H2O molecule to find moles of H. Then, we multiply the moles of C by the molar mass of C and the moles of H by the molar mass of H. Now, we know how much carbon and hydrogen there is in Aroclor. Then, we must subtract the mass of C and the mass of H from the total mass of Aroclor to find the mass of Cl in Aroclor. Next, we will divide the mass of Cl, C, and H by their respective molar masses to find the moles of each element present (we should already have the moles of C and H from earlier calculations). Finally, we will identify which element has the smallest number of moles and divide all the moles of each element by that smallest number to get the relative number of atoms of each element in Aroclor. I hope this helps!
To start this problem, we must first convert the grams of CO2 and H2O given to moles by dividing by the molar masses. Then, we can convert the moles of CO2 to moles of C as 1 mole of CO2 contains 1 mole of C. We do the same with water, but instead use the fact that there are 2 moles of H for every H2O molecule to find moles of H. Then, we multiply the moles of C by the molar mass of C and the moles of H by the molar mass of H. Now, we know how much carbon and hydrogen there is in Aroclor. Then, we must subtract the mass of C and the mass of H from the total mass of Aroclor to find the mass of Cl in Aroclor. Next, we will divide the mass of Cl, C, and H by their respective molar masses to find the moles of each element present (we should already have the moles of C and H from earlier calculations). Finally, we will identify which element has the smallest number of moles and divide all the moles of each element by that smallest number to get the relative number of atoms of each element in Aroclor. I hope this helps!
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