shychemist
shychemist:

bijoux-et-mineraux:

Kutnohorite - Kalahari Manganese Fields, Northern Cape Province, South Africa

I legitimately thought this was a scoop of strawberry ice cream at first.

Om nom nom nomThe color of this mineral is pale pink like strawberry ice cream because of a nominally Laporte-forbidden, spin-forbidden electronic transition between molecular orbitals which are both primarily derived from d atomic orbitals of manganese. The transition gives rise to a visible absorption only because of the relaxation of the selection rules associated with the mixing of the d orbitals with s and p orbitals. The small amount of s and p character allows a certain probability of a Laporte-allowed transition, albeit a low probability, which is why the color is not very intense.

shychemist:

bijoux-et-mineraux:

Kutnohorite - Kalahari Manganese Fields, Northern Cape Province, South Africa

I legitimately thought this was a scoop of strawberry ice cream at first.

Om nom nom nom

The color of this mineral is pale pink like strawberry ice cream because of a nominally Laporte-forbidden, spin-forbidden electronic transition between molecular orbitals which are both primarily derived from d atomic orbitals of manganese. The transition gives rise to a visible absorption only because of the relaxation of the selection rules associated with the mixing of the d orbitals with s and p orbitals. The small amount of s and p character allows a certain probability of a Laporte-allowed transition, albeit a low probability, which is why the color is not very intense.

shychemist

themageofd00m asked:

Question, If I have a strong base like NaOH (just assume complete dissociation) and it's concentration is only 4x10^-9 then what is the pH? Because it's a base it should be 14+log(4x10^-9), but that equals 5.602 which is an acidic pH? Please help me be less confused

shychemist answered:

The calculation is correct. I’ve gone through the calculations and gotten the same.

pH is dependent on concentration. I believe the reason the pH is low is because of how minute your concentration is.

But I think you have to consider the water the solution is in. Which would be at a pH of ~7. If you add the concentration of NaOH and what water would be at a pH of 7, the result is still near 7.

An example of this I found online here.

I hope this helps.

There are two chemical processes at play here: the dissociation of a strong base and the autoprotolysis of water. For solutions of strong acids and strong bases with concentrations greater than about 10^-5, the autoprotolysis of water has a negligible effect on pH. However, for dilute solutions of strong acids and strong bases, the amount of hydronium or hydroxide resulting from the autoprotolysis of water can be comparable to or greater than the amount contributed by the acid or base.

Consider the dissociation of NaOH first, since it’s so extremely favorable that it goes to completion regardless of any other simultaneous processes:

    NaOH —> Na+ + OH-

This process contributes 4x10^-9 M OH-.

Then consider the autoprotolysis of water, which is a dynamic equilibrium quantified by the equilibrium constant Kw = [H3O+][OH-] = 1.0x10^-14, and construct an equilibrium chart (aka ICE table):

2 H2O <==>       H3O+       +         OH-

Initial:                  0 M                4x10^-9 M

Change:               +x                       +x

Equilibrium:           x                4x10^-9 M + x

Then substitute the the equilibrium concentrations from the ICE table into the equilibrium expression:

Kw = [H3O+][OH-] = x(4x10^-9 + x) = 1.0x10^-14

Solve for x. (I’m not showing it here because it’s more math than chemistry, but basically you need to expand the polynomial and then use the quadratic formula, or a calculator if you prefer, like most of the kids do these days.) It turns out that x = [H3O+] = 9.8x10^-8.

Therefore, pH = -log[H3O+] = -log(9.8x10^-8) = 7.0

Essentially, the amount of hydroxide derived from the addition of NaOH to this water is negligible compared to the amount of hydroxide (or hydronium) that was already in the water due to autoprotolysis.

quantum-dragon

quantum-dragon:

cyclopentadiene:

NO HOMO
image

NO LUMO
image

silverwolf47

Nitric oxide didn’t listen to its chemistry teacher when told every atom in a stable molecule ought to have a full octet. NO didn’t blindly subscribe to the notion of doubly occupied HOMOs and vacant LUMOs. Instead, nitric oxide’s frontier orbital identifies as SOMO. It doesn’t conform to the established norms of diamagnetic chemistry that ascribe HOMO and LUMO labels to every molecule. NO is a proud, free-thinking, reactive species with unique properties and it’s not afraid to show off its extra anti-bonding electron to the world, even though some people consider it unusual or dangerous.

quantum-dragon

quantum-dragon:

psicologicamenteblog:

Source: Chemical structures of neurotransmitters.

Follow Francesca Mura on Pinterest

silverwolf47 got me dopamine earrings! ^.^

quantum-dragon, I was just about to tag you in this when you tagged me! Look at all the neurotransmitters!

By the way, I really wanted to get you serotonin earrings because it has a prettier chemic structure and is associated more with happiness and well being,but they were sold out.

I&#8217;m running a kinetics experiment to determine the order with respect to each reactant. Each NMR tube contains a different amount of each of two reactants. Monitoring the progress of the reaction in each tube over time will reveal how the reaction rate depends on the concentration of each reactant. Ideally, this information can offer insight into the mechanism of the reaction.

I’m running a kinetics experiment to determine the order with respect to each reactant. Each NMR tube contains a different amount of each of two reactants. Monitoring the progress of the reaction in each tube over time will reveal how the reaction rate depends on the concentration of each reactant. Ideally, this information can offer insight into the mechanism of the reaction.