Test 1 Question 7

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Jacy Black 1C
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Joined: Fri Apr 06, 2018 11:01 am

Test 1 Question 7

Postby Jacy Black 1C » Sun Apr 22, 2018 11:21 pm

Hello, I was wondering if someone could help explain how to correctly answer the following question from the first test:

"Determine the empirical formula for an organic compound that, when burned in the presence of oxygen, formed 8.45g of Carbon Dioxide and 1.73g of Water. What is the mass percentage of carbon and hydrogen in this sample?"

I am assuming that the sample must only consist of Carbons and Hydrogens, but I didn't know where to begin. Rather than having been given the percent mass, we are given the mass of the products, which confused me greatly. And and all help would be greatly appreciated!

Posts: 19
Joined: Fri Apr 06, 2018 11:02 am

Re: Test 1 Question 7

Postby Enzo_1I » Sun Apr 22, 2018 11:33 pm

Since you're trying to find the percent yield for this sample, you need to use (actual yield/ theoretical yield ) x 100%.
The problem gives you the actual yield (7.84 grams), so you need to find the theoretical yield which should be around 8.11 grams.
Then you can just plug in those number into the percentage yield formula.

Emely Reyna 1F
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Joined: Fri Apr 06, 2018 11:04 am

Re: Test 1 Question 7

Postby Emely Reyna 1F » Sun May 06, 2018 12:41 am

To find the empirical formula when you are given grams rather than percent mass you can start of by converting the grams into moles while also taking into account the ratio. For example take the 8.45 g of CO2 and divide by the molar mass to get mols of CO2 then use the ratio of 1 mol of C per 1 mol of CO2 to find the mols of C in CO2.

fara valdez
Posts: 48
Joined: Fri Apr 06, 2018 11:05 am

Re: Test 1 Question 7

Postby fara valdez » Sun Jun 10, 2018 11:04 pm

Just use conversions as you would grams to moles, except for the whole compound. Once youve reached that step in your conversion, then you isolate carbon in the CO2 conversion and Hydrogen in H2O.

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