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Topic: Stoichiochemistry marathon problem  (Read 3766 times)

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Offline JNW2

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Stoichiochemistry marathon problem
« on: March 22, 2016, 08:34:10 PM »
A 2.077-g sample of an element, which has an atomic mass between 40 and 55, reacts with oxygen to form 3.708 g of an oxide.
Determine the formula of the oxide (and identify the element).
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Offline Burner

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Re: Stoichiochemistry marathon problem
« Reply #1 on: March 22, 2016, 10:16:20 PM »
Hint: Consider the mole ratio of the elements in the oxide formed. Start by calculating oxygen mass in the oxide.
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Offline billnotgatez

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Re: Stoichiochemistry marathon problem
« Reply #2 on: March 23, 2016, 12:20:30 AM »
@JSK2
You have been on the forum for enough posts to know that you just do not post a question without some work shown.

You have to show your attempts or thoughts at solving the question to receive help.
This is a forum policy.
Click on the link near the top center of the forum page.
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http://www.chemicalforums.com/index.php?topic=65859.0

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Offline JNW2

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Re: Stoichiochemistry marathon problem
« Reply #3 on: March 23, 2016, 03:19:35 AM »
Quote from: billnotgatez on March 23, 2016, 12:20:30 AM
@JSK2
You have been on the forum for enough posts to know that you just do not post a question without some work shown.

You have to show your attempts or thoughts at solving the question to receive help.
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
http://www.chemicalforums.com/index.php?topic=65859.0
Attempt to solve problem:
oxygen weight =1.631 g and we have ratio of unknown element   and oxygen mass =2.077/1.631
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Offline Burner

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Re: Stoichiochemistry marathon problem
« Reply #4 on: March 23, 2016, 03:29:11 AM »
Quote from: Burner on March 22, 2016, 10:16:20 PM
Hint: Consider the mole ratio of the elements in the oxide formed.
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Year 1 science student in HKUST and a Chemistry geek.
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Offline AWK

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Re: Stoichiochemistry marathon problem
« Reply #5 on: March 23, 2016, 05:52:53 AM »
This is a case of simple chemical modelling.
Write down all common oxides from Ca (m=40) to Mn(m=55) and  compare mass ratios of oxygen to metal in these oxides to that one of your sample (or alternatively oxide to sample). Since this is modelling, two indications a better than one.
Best fit is the answer.
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AWK

Offline Burner

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Re: Stoichiochemistry marathon problem
« Reply #6 on: March 23, 2016, 06:23:19 AM »
Quote from: AWK on March 23, 2016, 05:52:53 AM
This is a case of simple chemical modelling.
Write down all common oxides from Ca (m=40) to Mn(m=55) and  compare mass ratios of oxygen to metal in these oxides to that one of your sample (or alternatively oxide to sample). Since this is modelling, two indications a better than one.
Best fit is the answer.

Well my method is to calculate the range of number of moles of the element in the oxide and then find out the only possible whole number mole ratio from it(I think it works, but this is my first time encountering this kind of problems).
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If I make any mistakes in the forum, please don't hesitate to correct me as I want to learn.

Offline JNW2

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Re: Stoichiochemistry marathon problem
« Reply #7 on: March 25, 2016, 06:10:05 AM »
Quote from: AWK on March 23, 2016, 05:52:53 AM
This is a case of simple chemical modelling.
Write down all common oxides from Ca (m=40) to Mn(m=55) and  compare mass ratios of oxygen to metal in these oxides to that one of your sample (or alternatively oxide to sample). Since this is modelling, two indications a better than one.
Best fit is the answer.
use your step the final compound is
V2O5 ,right?
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Offline AWK

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Re: Stoichiochemistry marathon problem
« Reply #8 on: March 25, 2016, 10:35:40 AM »
Good fit for both:  ratio oxide/metal and oxygen/metal
« Last Edit: March 25, 2016, 10:51:48 AM by AWK »
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AWK
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