## Chemistry Lab C

wec01
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### Re: Chemistry Lab C

BrownieInMotion wrote:
wec01 wrote:1. Write a balanced chemical equation for the reaction between calcium carbonate and hydrochloric acid.
2. Is this reaction exothermic or endothermic?
3. What molecule is produced that most greatly contributes to the answer in part 2?
1. $CaCO_3 + 2HCl \rightarrow H_2O + CO_2 + CaCl_2$
2. Exothermic.
3. CaCl2? Forming ionic bonds is usually very exothermic so CaCl2 should have a very negative Hf.
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### Re: Chemistry Lab C

What acid is called "white fuming" in its pure form?
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Dinoswarleafs
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### Re: Chemistry Lab C

BrownieInMotion wrote:What acid is called "white fuming" in its pure form?
Nitric acid =) I wanted to say Oleum/fuming sulfuric but then I remember sulfuric is in the name T_T

Why can oxygen gas produce magnetic properties under certain conditions? Provide a diagram to support your answer

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### Re: Chemistry Lab C

Dinoswarleafs wrote:
BrownieInMotion wrote:What acid is called "white fuming" in its pure form?
Nitric acid =) I wanted to say Oleum/fuming sulfuric but then I remember sulfuric is in the name T_T

Why can oxygen gas produce magnetic properties under certain conditions? Provide a diagram to support your answer
Oxygen is paramagnetic, meaning it has unpaired electrons in its ground state. This causes it to be weakly attracted to externally applied magnetic fields. Here's my MO diagram: [img]https://scontent-iad3-1.xx.fbcdn.net/v/t1.15752-9/s2048x2048/53026276_1224632847687883_2778410602865885184_n.jpg?_nc_cat=108&_nc_ht=scontent-iad3-1.xx&oh=98246a67ddb41b6f5088115b53a3b509&oe=5D22F4BC[/img]
Explain the observation that magnesium oxide is more soluble in aqueous magnesium chloride than in pure water.
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wec01
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### Re: Chemistry Lab C

BrownieInMotion wrote:
Dinoswarleafs wrote:
BrownieInMotion wrote:What acid is called "white fuming" in its pure form?
Nitric acid =) I wanted to say Oleum/fuming sulfuric but then I remember sulfuric is in the name T_T

Why can oxygen gas produce magnetic properties under certain conditions? Provide a diagram to support your answer
Oxygen is paramagnetic, meaning it has unpaired electrons in its ground state. This causes it to be weakly attracted to externally applied magnetic fields. Here's my MO diagram: [img]https://scontent-iad3-1.xx.fbcdn.net/v/t1.15752-9/s2048x2048/53026276_1224632847687883_2778410602865885184_n.jpg?_nc_cat=108&_nc_ht=scontent-iad3-1.xx&oh=98246a67ddb41b6f5088115b53a3b509&oe=5D22F4BC[/img]
Explain the observation that magnesium oxide is more soluble in aqueous magnesium chloride than in pure water.
Is it because the MgO, MgCl2 and H2O react to form MgOHCl which is more soluble than the initial MgO?
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### Re: Chemistry Lab C

wec01 wrote:
BrownieInMotion wrote:
Dinoswarleafs wrote:
Nitric acid =) I wanted to say Oleum/fuming sulfuric but then I remember sulfuric is in the name T_T

Why can oxygen gas produce magnetic properties under certain conditions? Provide a diagram to support your answer
Oxygen is paramagnetic, meaning it has unpaired electrons in its ground state. This causes it to be weakly attracted to externally applied magnetic fields. Here's my MO diagram: [img]https://scontent-iad3-1.xx.fbcdn.net/v/t1.15752-9/s2048x2048/53026276_1224632847687883_2778410602865885184_n.jpg?_nc_cat=108&_nc_ht=scontent-iad3-1.xx&oh=98246a67ddb41b6f5088115b53a3b509&oe=5D22F4BC[/img]
Explain the observation that magnesium oxide is more soluble in aqueous magnesium chloride than in pure water.
Is it because the MgO, MgCl2 and H2O react to form MgOHCl which is more soluble than the initial MgO?
I'm not actually sure if they would react that way. Here's what I was going for:
MgO reacts to form Mg(OH)2 in water:
$MgO \rightarrow Mg(OH)_2$

Mg(OH)2 then dissociates:
$Mg(OH)_2 \rightarrow Mg^{2+} + 2OH^{-}$

Addition of MgCl2 increases the solubility of MgO through the common ion effect, by driving the formation of more Mg(OH)2.
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wec01
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### Re: Chemistry Lab C

Oh yeah, I completely forgot about that.

Alright here's a question:
What is the half-equivalence point during a titration and what is the significance of the pH at this point?
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ThomasL
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### Re: Chemistry Lab C

The half-equivalence point in a titration is where the moles of titrant added is half the moles of the analyte. pH at this point is equivalent to pKa and represents the pH the buffer is optimized for buffering.
Also, regarding the magnesium oxide solubility question:
It seems to me that the common ion effect would decrease the solubility of MgO, for concentration of Mg(OH)2 is increased, and by Le Chatlier's Principle, the equilibrium would shift left. The cause would actually be the slightly acidic character of MgCl2 solution, with [Mg(H2O)6]2+ acting as the acid. The protons are able to react with both MgO and Mg(OH)2 and cause MgO to dissolve faster. There's some more information on this wikipedia page: https://en.wikipedia.org/wiki/Magnesium_oxychloride

wec01
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### Re: Chemistry Lab C

ThomasL wrote:
The half-equivalence point in a titration is where the moles of titrant added is half the moles of the analyte. pH at this point is equivalent to pKa and represents the pH the buffer is optimized for buffering.
Also, regarding the magnesium oxide solubility question:
It seems to me that the common ion effect would decrease the solubility of MgO, for concentration of Mg(OH)2 is increased, and by Le Chatlier's Principle, the equilibrium would shift left. The cause would actually be the slightly acidic character of MgCl2 solution, with [Mg(H2O)6]2+ acting as the acid. The protons are able to react with both MgO and Mg(OH)2 and cause MgO to dissolve faster. There's some more information on this wikipedia page: https://en.wikipedia.org/wiki/Magnesium_oxychloride
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2nd place Thermodynamics

ThomasL
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### Re: Chemistry Lab C

Thanks!
Explain why metallic conductors have positive temperature coefficients of resistance while semiconductors have negative ones.

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