Writing chemical formulas  [ENDORSED]

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Ryan Neis 2L
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Joined: Fri Sep 29, 2017 7:04 am

Writing chemical formulas

Postby Ryan Neis 2L » Thu Oct 05, 2017 10:02 pm

For questions when we are given the name of a compound, how can we write a chemical formula for it without the molecular formula of the compound being given?

Tess McDaniel 1F
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Re: Writing chemical formulas

Postby Tess McDaniel 1F » Thu Oct 05, 2017 10:03 pm

I remember Prof Lavelle saying in class that for this test you won't need to generate a chemical formula given just the name because we haven't learned nomenclature rules yet. He did say that we will need to know that by the next test I think though. Hope that helps!

Rachel Formaker 1E
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Re: Writing chemical formulas  [ENDORSED]

Postby Rachel Formaker 1E » Thu Oct 05, 2017 10:10 pm

When we are given the name of the compound in a problem and we are supposed to find the chemical formula for an equation with no other information, the compound is usually an ionic compound and we are supposed to be able to figure out the formula using the oxidation numbers of its elements.

For example, calcium chloride would be CaCl2 because Ca is in Group 2 and forms a 2+ ion, and Cl is in Group 7 and forms a 1- ion. Since compounds are electrically neutral, there must be 2 Cl- atoms to cancel out the charge of the Ca2+ atom.

However, we will not need to write chemical formulas this way for the test tomorrow.

Yashaswi Dis 1K
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Re: Writing chemical formulas

Postby Yashaswi Dis 1K » Thu Oct 05, 2017 10:53 pm


Just a quick question...when writing chemical reactions and balancing them, if there is a catalyst involved or heat being utilized for the reaction to occur, do we have to also place the catalyst's name above the arrow and place the triangle (representing heat being involved) above the arrow too? Please let me know when possible. I hope we don't lose points for that as long as the reaction is correctly balanced etc.

Thank you.


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Re: Writing chemical formulas

Postby Chem_Mod » Sun Oct 08, 2017 11:16 pm

Although the catalyst and heat symbols are very important in giving information about the complete chemical reaction (reaction conditions in general are important, often marked above the arrow if they are essential for the rxn to occur), they are not necessarily pertinent when simply balancing an equation. They may have an effect on the percent yield, but this should not have you loose points on the fundamentals exam.

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Re: Writing chemical formulas

Postby tiffanyteguh1C » Wed Nov 08, 2017 10:54 pm

What is the best way to write a chemical formula when you are given the molar mass and the reaction of a combustion reaction? (i.e. question 6 from test #1)

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