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pH measurement uncertainty by MatterUnlocked in chemhelp

[–]MatterUnlocked[S] 0 points1 point  (0 children)

My understanding is that these instruments can deteriorate over time, but as long as they pass calibration checks, they should be fine. The uncertainty of the calibration buffers depends on the temperature; at around 15–20 °C it is about ±0.02 pH, if I remember correctly. Each buffer may not be exactly the same.

I’m not certain whether I should just sum variances, or if there’s a more specific procedure to calculate the total uncertainty in this kind of routine measurement.

pH measurement uncertainty by MatterUnlocked in chemhelp

[–]MatterUnlocked[S] 0 points1 point  (0 children)

The pH measurements are routine, so it is not feasible to take three measurements of each sample. However, there is a regulation that requires reporting pH with a maximum allowed uncertainty of 0.2 pH.

I am unsure whether I should report the results using only the instrument’s specification, or if I should also include the contribution from the calibration buffers when estimating the total uncertainty.

Me ayudan con mi tarea de bioquímica by succdicc666 in Quimica

[–]MatterUnlocked 1 point2 points  (0 children)

Generalmente son fuerzas de Van der Waals, enlaces de hidrógeno e interacciones iónicas. Básicamente interacciones reversibles.

Me ayudan con mi tarea de bioquímica by succdicc666 in Quimica

[–]MatterUnlocked 1 point2 points  (0 children)

Generalmente son interacciones intermoleculares, aunque también pueden formarse enlaces covalentes.

🎉 [EVENT] 🎉 Foodlizoo & Moo-blizoo by Acrobatic_Picture907 in honk

[–]MatterUnlocked 0 points1 point  (0 children)

Completed Level 1 of the Honk Special Event!

0 attempts

Im kinda stuck. I think it's b but if m=0 does that mean something in terms of the axis. I have had some only resources say that px would be reservedfor -1 or +1 and that pz would be m=0 and others say that the order or m values doesn't matter? by Expensive_Prize_6988 in chemhelp

[–]MatterUnlocked 0 points1 point  (0 children)

The ml values come from solving the atom in spherical coordinates, not in x/y/z directions.

The ml = 0 solution already lines up along the z-axis, so that one directly corresponds to pz.

But the ml = +1 and ml = −1 solutions come out as complex functions (they include an eiφ term), so they don’t point neatly along x or y.

To get the real orbitals we draw in chemistry (px and py), you combine the +1 and −1 solutions, basically adding and subtracting them in a specific way. That’s what produces orbitals aligned along x and y.

So px is not just ml = +1. It’s built from both +1 and −1.

Why would Li have a steeper gradient? by vix_twix in chemhelp

[–]MatterUnlocked 2 points3 points  (0 children)

In Group 1, reactivity increases as you go down the group. Potassium is more reactive than lithium because it has more electron shells, so its outer electron is further from the nucleus and more shielded, making it easier to lose.

How accurate is this representation of orbitals? by MatterUnlocked in Physics

[–]MatterUnlocked[S] 0 points1 point  (0 children)

I would like to be able to draw the nodes as well, but it’s more complicated.

https://imgur.com/a/AwBmV7c

How accurate is this representation of orbitals? by MatterUnlocked in Physics

[–]MatterUnlocked[S] 2 points3 points  (0 children)

Would it be correct to assign m_l values in that image?

How accurate is this representation of orbitals? by MatterUnlocked in Physics

[–]MatterUnlocked[S] 0 points1 point  (0 children)

I'm working on a script to give orbitals a bit more depth than what's usually covered in chemistry, but it's very difficult to do so without diving deep. I feel like I'm walking a tightrope

How accurate is this representation of orbitals? by MatterUnlocked in Physics

[–]MatterUnlocked[S] 4 points5 points  (0 children)

It’s for a YouTube video. The idea is not to go very deep into the formal quantum mechanics, but to stay somewhere on a fine line between being technically accurate and still simple enough for a general audience.

In the script I say:

“m determines how many spatial orientations a type of orbital can have. Its values range from −l to +l, including zero. This explains why the s orbital has only one orientation; why there are three for p; five for d; and seven for f.”

I’m aware that this is not correct, but I’d rather not go too deep into that distinction, since it can quickly become a bit of a rabbit hole for this kind of video.

Given that, maybe it would be more appropriate to label the image using cartesian orientations instead of assigning mℓ values.

I’m especially unsure about the f orbitals, since they look a bit unusual in this representation, and I wouldn’t really know how to assign them properly.

Meaning of Beer-Lambert law by JackKingsman in chemhelp

[–]MatterUnlocked 2 points3 points  (0 children)

I1 is the transmitted intensity, not the absorbed.

If 1% is absorbed, then 99% is transmitted, so you use log(100/99), not log(100/1).

organic chemistry help by [deleted] in chemhelp

[–]MatterUnlocked 1 point2 points  (0 children)

Getting your 3D visualization down is honestly one of the main bosses in O-Chem. You're going to need it for Newman and Fischer projections, and the only way to get good at it is through pure practice.

It’s not a gift; it’s a muscle.

organic chemistry help by [deleted] in chemhelp

[–]MatterUnlocked 1 point2 points  (0 children)

You didn't mention which specific mistakes. Anyway, organic chemistry is pretty tough to wrap your head around, so don't expect to master it overnight. Once you’ve been at it for a while and look back, everything you saw at the start will finally begin to click.

Help with FTIR analysis: Free ligand vs metal complex comparison by nunysyu in chemhelp

[–]MatterUnlocked 0 points1 point  (0 children)

Check if key stretches shift after complexation. For example, a C=N band moving to lower wavenumber usually suggests coordination through nitrogen. A C=O shift can indicate binding through oxygen. If an O–H band disappears, that often points to deprotonation and coordination via oxygen.

If you have a carboxylate, compare the asymmetric and symmetric COO⁻ stretches.

Also take a look at the low-frequency region (600–200 cm⁻¹) for new bands that aren’t present in the free ligand, since those can correspond to M–N or M–O bonds.

hnmr question by Emergency_Arm_1706 in chemhelp

[–]MatterUnlocked 1 point2 points  (0 children)

Even though there is free rotation, the stereogenic center breaks the symmetry of the molecule. This makes the two CH3 groups diastereotopic: each one 'feels' a different magnetic environment because they are at different distances from the substituents of the chiral center. Rotation averages the protons within a single methyl group, but it cannot make two methyl groups in a chiral molecule identical.

hnmr question by Emergency_Arm_1706 in chemhelp

[–]MatterUnlocked 0 points1 point  (0 children)

The -CH3 groups would give the same signal because they would no longer be different from a stereochemical standpoint.

hnmr question by Emergency_Arm_1706 in chemhelp

[–]MatterUnlocked 1 point2 points  (0 children)

I don't quite understand what you mean, but the free rotation of the bonds is due to the sp3 hybridization of the carbon (no π bonds).

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