Potasium paramagnet

Experiment 16 Help!!! Experiment 15: The Determination of Iron(II) by Redox Titration Overview In this experiment, you used an oxidation-reduction (redox) reaction as a means of analyzing an unknown sample for how much iron(II) the sample contains. The experiment was performed over two weeks to give you a chance to take your time and get good results. During the first week of the experiment, you were given a solution of potassium permanganate, KMnO 4, of an approximate concentration which was to be used as the titrant (the solution in the buret). Potassium permanganate is highly reactive and is not available in a pure form. The solution you were given, therefore, could only be made up to an approximate concentration. Then, in the first week of the experiment, your goal was to determine the exact concentration of the KMnO 4 solution by reacting it with a pure, stable iron compound of known composition, ferrous ammonium sulfate (FAS). Potassium permanganate reacts with iron(II) salts according to the following oxidation-reduction equation 5 X (Fe 2+ Fe 3+ + e -) oxidation MnO 4 - + 8H + + 5e - Mn 2+ + 4H 2O reduction ___________________________________________________________________________ MnO 4 - + 5Fe 2+ + 8H + Mn 2+ + 5Fe 3+ + 4H 2O overall process By determining the exact mass of the FAS samples taken, and from the volume of KMnO 4 solution required to titrate those samples, the exact molarity of the KMnO 4 solutions could be calculate. In the second week of the experi...

This chapter gives a general introduction to NMR interactions in solids. More details on paramagnetic interactions of NMR, often dominating the spectra of paramagnetic solids, are then presented. A brief introduction to the first-principles calculations for NMR spectra of paramagnetic solids is also provided, which play an important role in spectral assignments. 1.1 Spin Interactions: A General Introduction The relationship of nuclear (electronic) spin and the magnetic moment. (a) For a nucleus with a positive gyromagnetic ratio, the positive sign of γ I leads to parallel alignment of spin and the magnetic moment. (b) For a nucleus with a negative gyromagnetic ratio or electron, the negative sign of γ I (or γ S) leads to antiparallel alignment of spin and the magnetic moment. The relationship of nuclear (electronic) spin and the magnetic moment. (a) For a nucleus with a positive gyromagnetic ratio, the positive sign of γ I leads to parallel alignment of spin and the magnetic moment. (b) For a nucleus with a negative gyromagnetic ratio or electron, the negative sign of γ I (or γ S) leads to antiparallel alignment of spin and the magnetic moment. Close modal For paramagnetic systems, where there are unpaired electrons, it is also important to describe the electronic magnetic moment, since these electrons will interact with the nuclear species of interest and have an effect on the NMR spectra (shift, linewidth, relaxation, etc.). Similar to the case for the nucleus, the elect...

We present an approach that allows detecting all three components of the residual magnetic field inside shielding, based on the electron paramagnetic resonance (EPR) of spin-polarized K atoms. The residual field experienced by spin-polarized K atoms dominates Larmor precession frequency, the smaller the frequency is, the more benefits it has to realize spin-exchange relaxation-free (SERF) regime under a definite spin-exchange rate. The measurements are accomplished based on depopulation . The EPR-based cross Introduction With developments of quantum manipulation technology and extremely weak signal detection and extraction technology, precision atomic magnetometry gets energetical development [1], [2]. Unlike traditional superconducting quantum interference devices (SQUIDs), there is no requirement to use liquid 4 He for cryogenic cooling. They are relatively convenient and inexpensive to set up and operate [3]. Among these magnetometers, spin-exchange relaxation free (SERF) magnetometer is the most remarkable one [4]. Romalis’ group from Princeton University had achieved the magnetic field measurement sensitivity of 0.16 fT/H z 1 / 2 in 2010 [5], which has already been used in the study of magnetoencephalography (MEG) [6] and magnetocardiography (MCG) measurements [7]. One characteristic feature of the magnetometer operated in SERF regime is that spin-exchange rate occurs much faster than Larmor precession rate [8], [9]. Generally, there are two ways to realize SERF regim...

Is there a difference in the paramagnetism value/effect between those elements like Cl that are exhibiting paramagnetism only because of the final unfilled sub-shell (3p in this case) in the p-orbital? In comparison to say Cr or Cu which have more sub-shells only partially filled and hence all 4s and 3d spins in the same direction? That is a good question, but its answer comes in two parts, and the second part requires some information you haven't encountered yet in order to answer fully. Ready? OK, here we go: (Part 1:) A single (isolated) Mg or Ca atom in its electronic ground state is diamagnetic, as you would predict from its ground-state electron configuration of (1s)2(2s)2(2p)6(3s)2. (Part 2:) However, a chunk of Mg or Ca metal contains a lot of Mg (or Ca) atoms. You haven't yet learnt about how the atomic orbitals (AOs) on one atom interact with the AOs on another atom to make molecular orbitals (MOs), but they do when the atoms are close enough -- and that's what leads to bonding (or not, depending on the interactions). It turns out that some of the interactions between the 3p orbitals on different Mg atoms can lead to molecular orbitals that are lower-energy overall than some of the 3s-only combinations, with the effect that some of the electrons in a chunk of Mg metal end up in 3p-based MOs, and can then have the same spin as some electrons in the 3s-based orbitals, for overall paramagnetism. We say that the 3s band of MOs overlaps the 3p band of MOs, leading to ...

EPR and magnetic susceptibility of potassium perchromate (K 3CrO 8) have been studied from liquid helium temperatures to 400 K. EPR spectra of dilute aqueous solutions of K 3CrO 8 yielded g iso=1.9712±0.0005, and 53 A iso=(18.6±0.5)×10 −4 cm −1. The (positive) sign for 53 A iso, deduced here from the dependence of the linewidths of hyperfine components on nuclear spin quantum numbers, constitutes the first direct experimental measurement of the (negative) sign of the unpaired electron spin density at a Cr 5+ nucleus. EPR spectra of powdered K 3CrO 8 doped in (diamagnetic) K 3NbO 8 and of K 3CrO 8 crystals yielded g ∥=1.9428±0.0005, g ⊥=1.9851±0.0005, A ∥( 53Cr)=+(36.3±0.5)×10 −4 cm −1 and A ⊥( 53Cr)=+(11±1)×10 −4 cm −1, the ∥ direction coinciding with the crystal c axis. These parameters establish that the unpaired electron orbital is the metal d x 2– y 2 orbital, with considerable charge transfer from the peroxy ligands. In concentrated samples, the EPR line shape is Lorentzian, providing direct evidence for electron spin exchange between Cr 5+ ions. Temperature dependence of magnetic susceptibility χ over 1.4 to 343 K follows the law χ(cm 3/mol)=[2.7933/( T+2.7)]+χ d, where χ d=−1.5×10 −4(cm 3/mol) is estimated to be the diamagnetic contribution. From the Curie–Weiss temperature of 2.7 K, an exchange coupling J=1.35 K between the Cr 5+ ions is estimated. The calculated exchange‐narrowed EPR linewidth is consistent with the experimental value of 15 G observed for K 3CrO 8...

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