Chemistry Lab C

[wec01]

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?

My attempt (Click to Show Hidden Text)

1. [math]CaCO_3 + 2HCl \rightarrow H_2O + CO_2 + CaCl_2[/math]
2. Exothermic.
3. CaCl2? Forming ionic bonds is usually very exothermic so CaCl2 should have a very negative Hf.

Yep, your turn!

[BrownieInMotion]

What acid is called "white fuming" in its pure form?

[Dinoswarleafs]

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

[BrownieInMotion]

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

I guess I'll go again :P (Click to Show Hidden Text)

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.

[wec01]

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

I guess I'll go again :P (Click to Show Hidden Text)

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.

Not sure but here's a guess (Click to Show Hidden Text)

Is it because the MgO, MgCl2 and H2O react to form MgOHCl which is more soluble than the initial MgO?

[BrownieInMotion]

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

I guess I'll go again :P (Click to Show Hidden Text)

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.

Not sure but here's a guess (Click to Show Hidden Text)

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:

Solution (Click to Show Hidden Text)

MgO reacts to form Mg(OH)2 in water:
[math]MgO \rightarrow Mg(OH)_2[/math]

Mg(OH)2 then dissociates:
[math]Mg(OH)_2 \rightarrow Mg^{2+} + 2OH^{-}[/math]

Addition of MgCl2 increases the solubility of MgO through the common ion effect, by driving the formation of more Mg(OH)2.

Your turn!

[wec01]

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?

[ThomasL]

My attempt (Click to Show Hidden Text)

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:

Idea (Click to Show Hidden Text)

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]

My attempt (Click to Show Hidden Text)

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:

Idea (Click to Show Hidden Text)

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

Looks good, your turn

[ThomasL]

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