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/sci/ - Science & Math

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2876679 No.2876679 [Reply] [Original]

Hey guys. Need some chemistry help (just grade 12/SCH4U)

Use standard enthalpies of formation to calculate the enthalpy changes in each:

1) Magnesium carbonate decomposes when strongly heated.

The sheet with the list of the formation values does not include Magnesium carbonate.

However, it does contain magnesium and oxygen. Also, what does Magnesium Carbonate decompose into? Magnesium, CO2? Magnesium, C, and O2?

Just a tip in the right direction would help.

Pic unrelated - THAT'S my specialty.

>> No.2876739

MgCO3 (+heat) ---> MgO + CO2

Same as limestone into quick lime.

You need to copy/scan the table of values then draw out a Hess's cycle, then we'll be able to help.

>> No.2876751
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2876751

>Pic unrelated - THAT'S my specialty.

You're in fucking highschool.. you guys don't even have majors yet.

When you are accepted to a PhD program for physics, then you can start saying it's your "specialty."

Also, lol at you being unable to figure out this basic chem problem.

>> No.2876799

>>2876751
Nice.

>>2876739
MgO = -601.7 kJ/mol
CO2 = -393.5 kJ/mol
MgCO3 = ??? kJ/mol

Thanks!

>> No.2876803

>>2876679
> Pic unrelated - THAT'S my specialty
> Pic: standard model particles
> High School Physics Student
wat

>> No.2876811

>>2876803
I said it was my specialty because I knew it'd draw people to my thread because the people here do care about some imaginary educational hierarchy.

I was hoping, though, you'd be able to help me with this chemistry problem.

>> No.2876826

>>2876799
You need to know the enthalpy of reaction, which the question should tell you. Then read this http://www.chemguide.co.uk/physical/energetics/sums.html#top

>> No.2876828

>mass
>eV
thefuckamireading.jpg
Last time I checked, we still measure particle mass in kg

>> No.2876830

>>2876811
I still remember learning this in school, but I cannot recall it. (Usually, we had all the intermediate steps given on our "enthalpy chart" or whatever it was.)

>> No.2876836

>>2876828
It's done for these particles
It isn't much fun working with 3 * 10^-1435252 numbers

>> No.2876837

>>2876828
We don't measure mass in kg but in units of mass. <span class="math">\mathrm{\frac{eV}{c^2}}[/spoiler] has mass dimension, and in natural units (which is consistently used all over particle physics) <span class="math">c=1[/spoiler].

>> No.2876855

>>2876826
I typed out the question verbatim. That's ALL the information I have.

There's a table in the back which tells the delta H values for MgO and for CO2, but not for MgCO3. I typed out the entire question.

>> No.2876884

BUMP