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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Why do ethanethiol molecules have strong london dispersion forces than that of ethanol?

I know that, molecules with higher molecular weights tend to make strong london forces.Is there any other reason which makes ethanethiol to have strong london dispersion forces ??
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11 views

Solvation rates of crystalline and noncrystalline materials

Assuming equal surface area (and other variables), would a highly ordered crystal of some substance dissolve more slowly or quickly than (or at the same rate as) a disordered sample of the same ...
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1answer
37 views

How does an air conditioner produce liquid [on hold]

I always notice that when an air condition is working and cooling the room it, is heating outside the room and a Liquid is dropping from the other side of the air conditioner. how does this happen and ...
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1answer
30 views

Raoult's Law and Mole Fraction

Raoult's Law states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the ...
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34 views

Why isn't Graham's Law working here?

In graham's law of diffusion most numericals I have seen assumes the formula $$\frac{r_1}{r_2}=\frac{P_1}{P_2}\sqrt{ \frac {M_2}{M_1}}$$ Where they say $P_1,P_2$ are the partial pressures of the ...
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22 views

What is first order reaction rate? [on hold]

Molecular iodine, $\ce{I2(g)}$, dissociates into iodine atoms at $625\ \mathrm{K}$ with a first-order rate constant of $0.271\ \mathrm{s^{-1}}$? What is the half-life for this reaction? (in s) ...
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20 views

Anomalous Electronic Configuration of Thorium

The electronic configuration of thorium ($Z=90$) is $5\mathrm f^0 6\mathrm d^2 7\mathrm s^2$. But, according to the aufbau principle, the electrons should first enter the $\mathrm f$ subshell and not ...
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0answers
16 views

Why is equilibrium constant unitless? [duplicate]

Why is equilibrium constant like kp and kc unitless? It should be unitless when the number of product and reactant molecules are equal but why is it so in other cases?
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73 views

How to explain the discrepancy between the calculated absorption wavelength within the particle in the box theory and the observed wavelength?

The experimental observed wavelength for this molecule is 425 nm. We are supposed to estimate this wavelength theoretically using this equation (energy change in a 1D box), where $N$ is the number of ...
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70 views

How to identify the number of pi electrons in a conjugated system to calculate the HOMO-LUMO gap with the particle in the box approach?

It's my understanding that for a particle in a 1-D box, the change in energy from the HOMO to LUMO can be approximated with the following equation: $$\Delta E=\frac{h^2 ( N + 1 )}{8 m_\mathrm{e} ...
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18 views

A mixture of 10 cm3 of methane and 10 cm3 of ethane was sparked with an excess of oxygen. What is the volume of CO2 gas produced at r.t.p.? [closed]

In the question they gave the volume of ethane and methane but temperature and pressure is not mentioned, so how can I possibly found the volume at room temperature and pressure of CO2? May be, I did ...
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10 views

Faraday's first law of electrolysis [closed]

Calculate the mass of substances deposited in a Cu electrode if a current of 0.2A is passed through the cell for 3 minutes
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13 views

Why is pressure or external force needed for combination of electron and proton in plasma phase?

I have studied that after rising temperature matter is converted into plasma. I want to know that whether in plasma phase nucleon coexist with electron but do not combine until pressure is applied. ...
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17 views

What is the proper way to calculate experimental error in this measurement?

I am working on error analysis of some of my measurements and have stumbled upon an issue with the propagation of error. According to this reading, The uncertainty of the average acidity ...
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0answers
11 views

Series Limit in a Spectral line

What exactly is a series limit in a spectral line graph? And do we talk about series limits for each series (eg. Lyman series in Hydrogen) or collectively for an atom? Is series limit the transition ...
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14 views

I need help Calculating the added amount of NaOH at each step and plot the titration curve? [closed]

if you can show me an example that would be greatly appreciated with the calculations. Thank you Burette Reading --- VolumeOf NaOH ------ pH 27.41------ ---------0.00------ -------3.39 ...
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13 views

Calculate the added amount of NaOH at each step and plot the titration curve? [closed]

if you can show me an example that would be greatly appreciated with the calculations. Thank you Burrete Volume pH reading Of NaOH (ml) added (ml) 27.41 0.00 ...
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2answers
41 views

What decides whether a reaction releases light or heat

I understand the reason that a chemical reaction would create photons (physics is more my strong point), but why would it create heat instead? My only guess is that the light released somehow causes ...
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14 views

How to calculate enthalpy change of neutralisation - what mass?

How to calculate enthalpy change of neutralisation - what mass? I made an experiment where I reacted 100ml HCL 2M with 100ml NaOH 2M in 1300ml Water, and got a temperature change dT. My question is ...
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16 views

What is the equivalent mass of fe in feS2? [closed]

The solution is M/11 Can you give explanation to reach this answer.
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69 views

Are there any colorful, odorless gases?

Gases are frequently described as "colorless, odorless, and tasteless." I am wondering if this is redundant, since I can't think of many gases that have a detectable color to begin with, much less ...
3
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1answer
72 views

Deriving an expression for dU as a function of V and T

I'm currently preparing for a physical chemistry exam tomorrow, and was given the following question for practice: Derive an expression for $\mathrm{d}U$ as a function of $\mathrm{d}V$ and ...
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2answers
56 views

Difference between microcanonical and canonical ensemble

I feel a little unclarity about this. Canonical ensemble is pictured as many systems in heat reservoir of infinite capacity having $N$ (number of particles), $V$ (volume) and $T$ (temperature) ...
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2answers
200 views

Why is activation energy temperature independent?

I know that activation energy for a reaction is the extra energy given to the reactants to reach the threshold energy so that they can collide and react. But then, why is it said that the activation ...
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0answers
17 views

Energy required to break salt bridges in peptides and proteins

Is there a way to calculate the energy required to break a salt bridge in a peptide or on the exposed surface of a protein in aqueous solution? Is there any useful literature on this topic? I'm ...
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1answer
52 views

Energy levels transitions of an electron?

I have an example that tells me that the energy transition between $n=1$ and $n=3$ is $12.1\ \mathrm{eV}$ using the following formula: $$E= -RH (\frac{1}{m^2} - \frac{1}{n^2})$$ and that the ...
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1answer
31 views

What is the relation between chemical thermodynamics and chemical kinetics? [closed]

Can one be understood on the basis of the other or are they not interrelated at all? The first thing my kinetics textbook demonstrated was how thermodynamics ignores time taken for a process whereas ...
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2answers
42 views

Clarify the meaning of Equivalent weight and its formula?

Actually, What is the meaning of Equivalent weight and How does its formula E=M/V supports the definition?
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33 views

Does the spin of an electron change when transferred from one atom to another?

Some atoms form bonds when they are given energy to create an excited state.From what I have learnt, every electron is assigned a specific spin quantum number. What I am curious to know,is that, is ...
3
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1answer
46 views

What is the meaning when it is said “Temperature of an Oxyacetylene Torch is 3500 degrees Celsius”?

I don't think flame is anything but the product at that temperature but I am not sure. What exactly is flame? And I think the correct statement should be that the exothermic reaction here produces ...
3
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1answer
71 views

Free energy of an ideal gas

I want to calculate the Gibbs free energy for an ideal monoatomic gas, i.e. $$U=\frac32nRT.$$ Free energy is defined as $G(T,p)=H-TS$ and using the definition of enthalpy $$G(T,p)=U+pV-TS=U+nRT-TS.$$ ...
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21 views

Crystal defects involving electroneutrality violation

Is there any example of a non-stoichiometric defect in crystal lattices which involves electroneutrality violations (i.e., the system itself ends up having unbalanced charge which may be neutralized ...
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1answer
66 views

General expression for entropy and free energy

The specific heat capacity of a solid at constant pressure and low temperatures is given by $$c_p=aT+bT^3$$ with $a$ and $b$ are constants. How can I calculate a general expression for the entropy ...
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106 views

Sodium chloride and melting of the ice

My question is this, In European countries, they use NaCl or KCl to melt ice during the winter season. In Asian Countries, they use NaCl to keep the ice without melting. (Ex- Ice cream boxes, Beer ...
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55 views

Liquid nitrogen superheating with a layer of oil?

edit: Thanks Ivan, also further research. Pure water can be superheated to a few degrees above 100 degrees. However I remember reading reading that water can be superheated to even higher ...
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0answers
39 views

When dispensing liquid nitrogen, why does the surface get wet rather than frozen?

When I go to dispense liquid nitrogen after someone else has just used it (say in the last 30 minutes or so), the copper pipe used to transfer the liquid is covered in frost/ice. This makes sense, ...
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2answers
65 views

How does one determine the probability of H⁺ to H₂O in pure water?

The ratio of $\ce{H+}$ to $\ce{H2O}$ is something around $10^{-8}$. How did people determine that? You cannot use the $K_\mathrm{w}$, $\mathrm{p}\ce{H}$, $\ce{[H+]}$ ion concentration value to answer ...
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1answer
86 views

Rocket propellants: accuracy of vapor pressure estimation techniques

I would like to determine the vapore pressures of a couple of substances (rocket propellants) over a significant temperature range within a ~10% error margin. For a first test, I tried to ...
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1answer
32 views

Chemical potential and it's implications in an open system

Take the fundamental equation for the Gibbs free energy of a system: $$dG=VdP-SdT+\sum_i\mu_idn_i$$ Thus, the chemical potential can be defined in terms of the Gibbs free energy as follows: ...
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1answer
67 views

chemical kinetics of a reaction, rate constant, activation energy

From the Arrhenius equation in kinetics of reactions, $$k = A\exp{\left(-\frac{E_\mathrm{a}}{RT}\right)}$$ Which tells us about the Temperature dependence on rate constant of a reaction. Activation ...
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0answers
56 views

n-Butane, isobutane and propane [closed]

This questions is related to the condensation of the three flammable gases above. We respond to illegal clandestine drug labs where the lab operators are putting butane cans inside the freezer to ...
3
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0answers
52 views

Real Gas - Van der Waal's Equation

The Van der Waal's Equation for a real gas is: $$RT=(P+\frac{a}{V_\mathrm{m}^2})(V_\mathrm{m}-b)$$ We have understood this formula by saying that $a$ is the term which is for force of attraction ...
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1answer
59 views

How does changing volume affect concentration of solutions?

My teacher performed an experiment and made us watch. He prepared 3 conical flask containing 50 mL mixture of sodium thiosulphate, potassium iodide and acetic acid. He also had 3 measuring ...
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2answers
39 views

can anyone suggest me good chemistry video lectures [duplicate]

Can anyone please suggest me some websites from where i can get free chemistry video lectures?it must be relevant to iit jee syllabus.
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41 views

Why do chlorinated silanes have lower boiling points than their methane analogs?

The boiling points of the chlorinated silanes and methanes are given below: $$\begin{array}{ccc} \hline \text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
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31 views

If something reacts with oxygen, when calculating the empirical formula, do you use O or O2? [duplicate]

There was a question which I attempted, which stated: Sodium burns in oxygen to give a pale yellow solid X (Part a) $1.73 ~\mathrm{g}$ of sodium reacts with $1.20 ~\mathrm{g}$ of oxygen. ...
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40 views

Endothermic reactions with significant activation energy

Are there any chemical reactions where in order to induce the reaction, you have to heat up a substance but after the reactions happens, the substance is much colder than even before you started ...
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33 views

Enthalpy change and equilibrium

I don't understand why enthalpy change won't change at an equilibrium? The reason I ask this is because of this question: At first I thought the answer is C, but I realised that the amount depends ...
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2answers
49 views

Why is partial pressure proportional to mole fraction in Henry's law?

According to Henry's law of partial pressure, partial pressure of a gas above a solution is directly proportional to the mole fraction of the gas in the solution. But my question is: If the mole ...
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0answers
30 views

Tetrahedral arrangement of particles in cubic unit cell

What is arrangement (diagrammatically) of particles (atoms) in cubic unit cell so that I can correctly find out the radius ratio?