post test problem

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Dakota Walker 1L
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Joined: Wed Sep 18, 2019 12:17 am

post test problem

Postby Dakota Walker 1L » Thu Oct 10, 2019 1:39 pm

In the post module test there was a question asking the following: 339.20 g of Cobalt metal is reacted with Fluorine gas to produce a compound with a mass of 996.08 grams. What is the empirical formula of this new compound? I was wondering if you always apply the law of conservation of mass to these problems even when a gas and a different compound is created?

Tiffany Vo 3G
Posts: 52
Joined: Sat Aug 17, 2019 12:17 am

Re: post test problem

Postby Tiffany Vo 3G » Thu Oct 10, 2019 1:51 pm

The law of conservation of mass should apply to all problems, so you should be able to subtract the mass of cobalt from the final compound's mass to find the mass of fluorine gas originally involved in the reaction. After finding the mass of the fluorine, you should be able to convert each of those compounds into moles using the molar mass and divide by the smallest value of moles to get your empirical formula.

Shail Avasthi 3C
Posts: 86
Joined: Fri Aug 30, 2019 12:17 am

Re: post test problem

Postby Shail Avasthi 3C » Sat Oct 12, 2019 5:21 pm

Yes, understanding conservation of mass is key to solving this problem. The amount of Cobalt is unchanged in the reactants and products, so to find the mass of Fluorine used, you need to subtract the mass of Cobalt (339.20 g) from the final mass of the products (996.08), which you can use to solve the problem. Note that the mass of the products (996.08) has to be the same as the mass of the reactants.

Caitlin Ciardelli 3E
Posts: 44
Joined: Wed Sep 18, 2019 12:19 am

Re: post test problem

Postby Caitlin Ciardelli 3E » Sun Oct 13, 2019 11:03 pm

You are correct. For these types of problems, conservation of mass is essential!. The mass of Cobalt needs to be the same between reactants and products. You can then find mass Flourine by having total mass - cobalt mass (339.20 g - 996.08). This will give you the mass (in grams) of cobalt! Hope this helps


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