Questions tagged [physical-chemistry]

The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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Chemistry involving lab [closed]

I am having problems finding:: Percent silver in alloy? Mass of copper in copper oxide? Mass of copper in alloy? Percent copper in alloy?
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Interpreting phase diagram of mixture of partially-miscible liquid that boils before complete mixing

Source: Atkins' Physical Chemistry, 8th Edition, P.188 This is an example given by the stated reference book. Interpretations on this phase diagram is given. An extract of the interpretations is ...
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382 views

White hot hydrogen gas, like that during a big bang

Difficult to know for certain which field this is. According to what I can discover about it, the big bang explodes into being as white hot hydrogen gas, millions of degrees hot. I'm okay with that ...
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Different products using different indicators

A question states that 0.1 M solution of compound$$\ce{Na2CO3.NaHCO3.2H2O}$$ is titrated against 0.05M HCL, and that a different amount of HCL is used according to the indicators(phenolphthalein or ...
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Question on chemical equilibrium

8 moles of so2 and 4 moles of O2 are mixed in a closed vessel.the reaction proceeds at constant temperature. By the moment when equilibrium sets in,80% of the initial amount of so2 enters into the ...
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1answer
246 views

Calculating exposure time to inactivate coronavirus by UV light

Sorry for a layman question. I'm having difficulties understanding some basic math apparently. According to a paper, for a coronavirus, the UVGI dose for 90% inactivation is 339–423 μW sec/cm2. I ...
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What would be the effect of the addition of an inert gas to a reaction at equilibrium?

Why does a dissociation reaction shift to the right with the addition of an inert gas? (I am still new to the topic of equilibrium, so please explain in simple words.)
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How do you manage to liquefy a gas by applying only pressure?

How can you liquefy a gas by applying only pressure? To increase the pressure of a gas you need a compressor, and when the compressor does work on the gas , it will increase his pressure but at the ...
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1.00 × 10^18 formula units of LiCl =? [closed]

How many total moles of ions are released when the following sample dissolves completely in water? 1.00 × 10^18 formula units of LiCl = ??
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What exactly is temperature?

I've read at many places that temperature is the average kinetic energy of particles present in an object. I just don't intuitively get how kinetic energy is connected with temperature. And how is ...
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Colligative properties of colloids

The following lines are from my textbook: Colloidal particles being bigger aggregates, the number of particles in a colloidal solution is smaller than a true solution. Hence, the values of ...
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What is the formula for migration rate of DNA in agarose gel electrophoresis?

Let's consider a typical agarose gel electrophoresis experiment. An appropriate quantity (not so much that it is overloaded, but not so little that it cannot be visualized) of linear DNA pieces with ...
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A question about potential difference across a membrane

Membrane potential of living cells arising from the difference of concentration of ions on both sides of the membrane, but why didn't someone use selective polymers as AEM (Anion Exchange Membrane) ...
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How can we define a non-spontaneous reaction?

Consider a reaction:$$\ce{$aA + bB$ <=> $cC + dD$}$$ The value of reaction quotient at a certain time $t$, $${Q_c = \frac{[C]^c[D]^d}{[A]^a[B]^b}}$$ where the concentrations $[A], [B], [C]$ and ...
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How can we compare two orbitals in terms of energy with different n and l values? Why are there energy differences? [closed]

While reading from my book I read that in the transition metals the d orbital is filled up before the p orbitals and this was due to the d orbital being lower energy. My question is, why is this the ...
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Symmetries and degeneracies of the s,p, and d orbitals

Consider the molecular AB_8 (complex with central atom A and 8 B ligands (coordination number 8), for which I determined the point group D_4d) and determine the symmetries and degeneracies of the s, p,...
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Grouping of symmetry classes in chemistry character tables

In the C3v point group, it lists three sigma Vs together in one column (class), and it doesn't list the cVs separately. Consequently there are three irreducible representations. In the C2v point ...
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Water-Soluble Photoinitiators for Free-Radical Photopolymerizations?

Could anyone recommend me a good proven free-radical photoinitiator available commercially suitable for (meth)acrylate-based UV-light photo-polymerizations ocurring in water phase, preferably with ...
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Concentration of gas above aqueous ammonia

I am a physicist who has run into some chemistry in the lab (and unfortunately, I've completely evaded any formal training in chemistry). I have exposed some samples (I think details of the sample are ...
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Solving a quadratic equation for pressure of real gas with unknown volume

Question Calculate the pressure exerted (in atm) by 1 mole of $\ce{CH4}$ gas at a temperature of $\displaystyle\pu{\frac{24}{0.0821} K}$ if volume occupied by $\ce{CH4}$ molecules is negligible. ...
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Why are there only 2 peaks in proton NMR of 2-iodopropane? [closed]

I was reading about proton NMR and was drawing high resolution spectra for some of the molecules. I have currently drawn proton NMR spectra for ethanol and ethyl benzoate and got number of peaks as ...
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Calculate the heat of formation [closed]

How to Calculate the heat of formation of formaldehyde (HCHO) at 350 K. The standard generation heat is -119 kJ mol-1. The values of the heat capacity (Cp) for constant pressure: formaldehyde: 19.3 J ...
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Effect of optical isomerism on colour of transition metal complexes

I know that different stereoisomers of a given transition metal complex (cis- and trans- forms) have different colours. But do different optical isomers (non-superimposable mirror images) have ...
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Relation between enthalpy, entropy and Gibbs energy at thermal equilibrium

$${\Delta S_{total} = \Delta S_{sys} + \Delta S_{surr}}$$ ... Equation (i) If system is in thermal equilibrium with the surrounding i.e. ${T_{sys} = T_{surr} = T}$ Increase/ decrease in enthalpy of ...
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Rates of heterogeneous surface reactions [closed]

This is a question I've been trying to solve for a while, but I haven't taken chemical kinetics yet and just can't seem to figure it out. I have the following reaction: $$\ce{CO2 + ^{\ast} <=> ...
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Comparison of acidity of aqueous solutions of Lewis Acids

What can be the order of acidity of aqueous solutions of following Lewis acids: $\ce{FeCl3, AlCl3, BeCl2, NiCl2}$ The simplified reactions are: $\ce{FeCl3}$: $\ce{FeCl3 + 6H2O -> [Fe(H2O)6]^3+(...
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How to deal with the unit “Coulomb per equivalent”? [duplicate]

In a question that I came across they defined $1\,\pu{F}$ as 96500 coulomb per equivalent. Now as far as my knowledge is concerned $1\,\pu{F} = 96500\,\pu{C/mol}$. The question involved asks to ...
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Which substances have the highest/lowest enthalpy of formation per gram?

Which substances have the most extreme enthalpies of formation per gram at standard temperature and pressure?
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Reason for the formation of azeotropes

Why is it that some liquid mixtures (that exhibit positive/negative deviation from Raoult's law) form azeotropic mixtures at certain compositions? What is the physical reason behind this; are there ...
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Combining enthalpies of formation and combustion in the context of Hess's law

I know that you can use enthalpy of combustion to work out formation, and Formation to work out enthalpy change. But can you use enthalpy of formation and combustion data is the same Hess's cycle to ...
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State of matter, varying pressure and volume we see a drastic change in solids, as we see in gases and liquids? [closed]

Imagine a solid of a single dimension, to obtain its heat capacity at constant volume $C_p=\frac{\partial U}{\partial T}$ and the constant pressure $C_v=\frac{\partial H}{\partial T}$. It is known ...
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Why is the ionic product of water $K_w$ the same in acid, water, and alkali?

Seen on the web: The concentration of [H+] and [OH−] both vary based on the the composition (acid/alkaline) of the solution, but the remarkable thing is that their product does not. When [H+] goes ...
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What is this formula? CO2 + 4 H2 = CH4 + 2 H2O [closed]

1) How many moles of H20 can be produced from 12. 5 moles of CO2? 2) How many moles of CH4 can be produced along with 5.25 moles of H20?
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Why is the carbon monoxide triple bond stronger than the nitrogen-nitrogen triple bond?

The $CO$ triple bond has a bond enthalpy of 1072 kJ/mol while the $N_2$ triple bond has a bond enthalpy of 945 kJ/mol, at least according to my source. The molecules are isoelectronic, so I couldn't ...
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Using Dalton's law of partial pressures

A container of volume $\pu{4.0 L}$ contains nitrogen at $\pu{25 °C}$ and $\pu{803 kPa}.$ This container is connected by a valve to another container of volume $\pu{10.0 L}$ that contains argon at $\pu{...
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Calculating Enthalpy Changes at Different Temperatures

To calculate $\Delta H$, the change in enthalpy at $\mathrm{100^\circ C}$ for the reaction below, one needs what addition information? $$\ce{N2(g) + 3H2(g) -> 2NH3(g)}$$ $\Delta H^\circ = ...
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How can I calculate Kp given Gibb's free energy? [closed]

I need to solve a problem but I can't seem to figure out how to move from the given values to Kp. Here's the question: 2SO2(g) + O2(g) ⇌ 2SO3(g) ΔrH° = −200 kJ.mol-1 and ΔrS° = −187 J.mol-1.K-1 at ...
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Limiting molar conductivity of multiple solutes

Suppose there is a water solution at $\pu{25 °C}$ with $\ce{Na+},$ $\ce{Mg^2+}$ cations and $\ce{Cl-},$ $\ce{HCO3-}$ anions. Concentrations $[\ce{Na+}],$ $[\ce{Mg^2+}],$ $[\ce{Cl^-}]$ and $[\ce{HCO3-}]...
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What is the lattice enthalpy of zinc chloride?

I am trying to find a literature value for the enthalpy of solution of zinc chloride to compare with my experimental value but I can't seem to find it. So I'm trying to use the formula: enthalpy of ...
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Network covalent bonds during melting

What happens to the intramolecular bonds when a network covalent substance is melted? I understand that in covalent molecular substances, the intermolecular bonds weaken between the molecules once ...
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How do I distinguish between internal energy and enthalpy?

I am finding it hard to distinguish between the two. Can someone explain the two terms and the difference between them? I tried learning from Wikipedia, but it said for both the above terms that it ...
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However what is so acidic about CaO and basic(no pun intended) about SiO2 while calculating basicity of slag?

I have seen Basicity to be calculated as $\mathrm{B} = wt\%\:\ce{CaO}/wt\%\:\ce{SiO2}$ particularly in slag bascity/acidity calcuations. Now I do not think that $\ce{CaO}$ is the most basic oxide that ...
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551 views

Entropy and enthalpy at the melting point of benzene

For the melting of Benzene, since it is melting, it feels intuitive to think that the change in entropy will be positive (more disorder) and enthalpy will be positive (exothermic). However, when I ...
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What exactly are the graphs of orbitals?

In my QM class we are finding the wave functions of the hydrogen atom. In spherical coordinates, these wave functions are functions of 3 variables: $r,$ $\theta,$ and $\phi.$ My professor stated that "...
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Electron transfer rates in Marcus Theory [closed]

Electron transfer rates (k) as derived from Marcus theory assumes i) thermal equilibrium and ii) neglects quantum nature of low-frequency phonon modes. Can anyone explain what is at the heart of these ...
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Having a contradiction while deriving Gay-Lussac's law using Boyle's law and Charles' law

From Boyle's law: $$P_1V_1 = P_2V_2 \quad\implies\quad V_2 = \frac{P_1V_1}{P_2} \label{eqn:boyle}\tag{1}$$ From Charles' law: $$\frac{V_1}{T_1} = \frac{V_2}{T_2} \quad\implies\quad V_2 = \frac{...
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Relationship between auto-ignition temperature with pressure and fuel

Experimentally it appears that increase in pressure, fuel concentration, and chain length causes AIT to decrease until a minimum where even further increase in these parameters increases the AIT. ...
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Entropy - “Wiggle”?

The title is not a reference to a Jason Derulo song. In any case: 1) How is change in entropy measured, experimentally? I've Googled this for a bit and I've found all sorts of mathematical ...
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What happens if the filter paper in vacuum filtration is BIGGER than the buchner funnel diameter? [closed]

I’m wondering what would happen if the filter paper in a vacuum filtration process is bigger than the buchner funnel diameter? I mean would some differences occurs? Or would the whole experiment ...
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Why does the heat of formation of organic radicals and positive ions decrease with their size and degree of branching at the radical or ionic site?

I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following: The heat of formation ...

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