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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12 views

Relation ship between differential rate and rate law

Say for a reaction, aA+bB --》cC+dD We have, Rate=k[A]^a[B]^b and by differential rate law we have, -d[A]/adt = -d[B]/bdt Now how we relate these two. ALSO REFER THE PICTURE ADDED PLEASE
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29 views

Rate of reaction of copper poweder with nitric acid [on hold]

Why is the reaction of nitric acid with copper powder initially not fast but it becomes rapid after some time? I have no idea on this one. How does copper reduce dilute nitric acid to nitric oxide ...
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48 views

Electrolytic cell - Potentials

I'm an electronic engineer student and I'm trying to understand the basics of electrolytic cells and practical values' meaning. Based on my figure and electrode potencial values (Vce, Vre and Vwe), ...
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1answer
116 views

Finding the isotherm with given minima

Get the temperature of the isotherm for water for which the local minimum is at $\pu{100 Pa}.$ Use the values of $a$ and $b$ of water. My approach In the van der Waals equation, set $$\frac{\...
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18 views

Change in concentration of 1st order reaction [on hold]

For the first order reaction $\ce{A → B},$ is the change of concentration of $\ce{A}$ equal to the change of concentration of $\ce{B}$? And would this be different if you have $\ce{A → B + C}\,?$
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How to calculate pH of final solution using volume and pH of initial solutions? [on hold]

When two solutions of equal volume with pH 2 and 8 are mixed, what happens to resulting pH ? How to calculate the final pH? I am being too specific this time.
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1answer
27 views

Numerical simulation and calculations of pH

a. Reaction of $\ce{CO2}$ addition in water is as follows: $\ce{CO2}$ + $\ce{H2O}$ $\ce{->}$ $\ce{H2CO3}$ b. Then, pH of $\ce{H2CO3}$ solution is increased to 12 by addition of 1M $\ce{NaOH}$. ...
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13 views

Spectroscopy and Chromatography [closed]

25 cm^3 of an unknown solution has an absorbance of 0.3. Added is 5 cm^3 of a solution of the same compound (concentration = 10 ppm) and absorbance is now 0.34. Calculate the original unknown ...
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25 views

Measuring change in concentration of hydrogen peroxide

I am conducting an experiment to find the rate constant of the decomposition of hydrogen peroxide, $\ce{H2O2}.$ For this, I was planning on using the integrated rate law: $$\ln(\text{final ...
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1answer
67 views

How do I solve this problem on Mole balance?

Zinc oxide is reduced at a constant temperature in a closed reactor using ZnO(s) and C(s) as the only starting materials.The following reactions are assumed to be at thermodynamic equilibrium. $ZnO(s)+...
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42 views

Calculating ionic strength and pH of a buffer solution [on hold]

Im trying to calculate ion strength and pH of solution. Components of the solution: 47 ul of 1000 pmol DNA in Elution Buffer (10 mM Tris-HCl pH 8.5) was bound to 3 ul of 10 µM YoYo1 (flourescent dye) ...
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27 views

Two methods for calculating ΔH yield different results [on hold]

A problem in my book says: $\pu{140 g}$ of $\ce{N2}$ (perfect gas) changes from $\pu{200 K}$ to $\pu{400 K}$ at constant volume. Calculate the change in internal energy $\Delta E$ and the change in ...
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8 views

Lattice Energy of MX2 type

While finding the solution to the question that which among BaO and BaCl2 has hi that is energy I found that it was BaO whose lattice energy is high and there were explaining it just with charges. So ...
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17 views

More shells as principal quantum number increases [closed]

Why do more shells open up as n increases? As in why does n = 1 only have 1s but n=3 have 3s, 3p, 3d? Does it have something to do with the magnetic quantum number?
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1answer
236 views

Is the equation dG = Vdp − SdT valid only for a reversible process? Can it be applied for an irreversible one too?

In the derivation, we write: $$ \begin{align} G &= H - TS &\quad&\to&\quad \mathrm dG &= \mathrm dH - T\,\mathrm dS - S\,\mathrm dT \\ H &= U + pV &\quad&\to&\quad ...
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1answer
44 views

Find the masses of NaCO3 and NaHCO3 in a mixture of NaCO3/NaHCO3 by using titration data [closed]

I'm having difficulty finding answer for following question: ]2 I am having difficulty in solving the last part about finding in 1 litre I used $n_1v_1=n_2v_2$ to equate equivalent and find molarity ...
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2answers
32 views

Why does a NOx container get cold when NOx is released? and What is the relationship of the vapor pressure curve with the liquid-vapor dome?

The temperature at which $\ce{NO_x}$ is in equilibrium with its liquid and vapor phase at 1 atm is about –84 °C. Does that mean $\ce{NO_x}$ exists as a liquid at that temperature? What about it's ...
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1answer
35 views

Is the density of solute same as the density of solution? [closed]

This problem came up while solving some problems on mass percentage and mole concept. Essentially, our teacher said that the $w/w\%$ and the $v/v\%$ for a given solution will be the same, because in ...
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28 views

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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2answers
89 views

What is the origin of the Quadratic factor in calculation of XRD peaks?

Whenever we are to calculate the d-spacing(for cubic system) in XRD peaks with reference to Quadratic Factors we do that with the help of the formula $$\frac{1}{d_{hkl}^2}=\frac{h^2+k^2+l^2}{a^2}.$$ ...
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32 views

Fick's second law atomic diffusion question [closed]

I have a question about diffusion and i'm not sure how to tackle it. A new processing method is being tried for a lithium battery cathode material -LiCoO2. the process leaves the ceramic oxygen ...
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1answer
47 views

Strength of bases and acids

Is it possible that strong acids like H2SO4 behave as weaker ones like CH3COOH when the concentration is really high and vice versa for weak acid? And same question for bases. By this I am generally ...
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1answer
39 views

How to prove it mathematically that either rhombic or the monoclinic sulfur is denser?

For the transition, rhombic sulfur → monoclinic sulfur, the value of $ΔS$ is positive. The transition temperature increases with increase in pressure. Which is denser, the rhombic or the monoclinic ...
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336 views

How do I solve such questions on paramagnetism and ferromagnetism?

Match the type of magnetism given in Group I with the material given in Group II: $$ \begin{array}{ll|ll} \hline & \textbf{Group I} & & \textbf{Group II} \\ \hline \text{P} & \...
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24 views

Why is there minus sign on dP/dt when deriving the equation for effusion?

I just want to the reason behind minus sign on dP/dt. I'm able to workout the rest of the derivation.
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47 views

Finding initial mole fraction of ammonia in ammonia-hydrazine mixture using thermodynamic parameters before and after thermal decomposition

A mixture of $\ce{NH3}$ and $\ce{N2H4}$ is placed in a sealed container at $\pu{300 K}$. The pressure within the the container is $\pu{0.6 atm}$. The container is heated to $\pu{1000 K}$ where the ...
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3answers
85 views

$K_c$ vs $K$ in equilibrium reactions

I don’t understand why the following question The decomposition of nitrosyl bromide $(\ce{NOBr})$ proceeds by the following reaction: $$\ce{2 NOBr(g) <=> 2 NO(g) + Br2(g)} \qquad K = 0....
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2answers
40 views

Rate law for breakdown of ozone to oxygen

For the following problem: Example 3: Write the rate law for $\ce{2 O3 -> 3 O2}$ given that the f‌irst step is fast and reversible, and the second step is slow. $$ \begin{align} &\text{...
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1answer
52 views

Relationship between Gibbs free energy and potential energy (related to reaction coordinate diagrams)

For a rate law, the rate constant $k$ is given by the equation $$\ln k = \ln A - \frac{E_\mathrm{a}}{RT}\tag{1}$$ If $k_\mathrm{fwd}$ is the forward rate constant and $k_\mathrm{rev}$ is the reverse ...
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1answer
55 views

Is the cathode and anode on the cell notation of an Electrolytic cell on the same side as if how you will write it for a Galvanic cell?

I was reading an online material then I came upon a cell notation for an electrolytic cell (I determined that it was an electrolytic cell because of the absence of a salt bridge). Usually, I will ...
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22 views

How are standard enthalpy of formation values determined?

How are standard enthalpy values of formation determined? And how do you determine other enthalpies, such as the enthalpy of hydration? I'm really confused as to where they got their numbers from.
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22 views

How can I calculate for the theoritical potential needed to precipitate a metal in an electrolytic cell?

We were given a problem where we are to calculate the theoretical potential needed to initiate the deposition of $\ce{Cu^2+}$ in a solution buffered to $\mathrm{pH} = 4.00$ and the IR drop associated ...
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Book reference for chemical equilibriums [duplicate]

I need to practice more chemistry equilibrium questions but most of the books contain only theory parts and not enough questions. so can please recommend me a question book.
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1answer
39 views

Long term composition of matter [closed]

If I have an igneous rock shown by geologic study to be 10,000 years old, approximately what percentage of the atoms (or protons, etc) in the rock might be the same ones that were in it 10,000 years ...
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1answer
41 views

Cathode ray discharge tube

I am learning about 'cathode ray discharge tube'. I know when electrons are given out from cathode, they travel to anode, because anode being positively charged attract those electrons and continue to ...
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41 views

Finding a Certain Coolant [on hold]

Is there a highly endothermic chemical with a thermal conductivity coefficient greater than 0.1 that could be exposed to 600 degrees Celsius but only heat up to 100 degrees Celsius? Preferably, this ...
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1answer
82 views

Can precipitation reactions attain equilibrium?

While studying about the characteristics of Chemical Equilibrium, I came across a point in my book which read A chemical equilibrium can be established only if none of the products is allowed to ...
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1answer
70 views

How do I determine molality from mole fraction without knowing how much of the solution I have?

What is the value of $x$ if $x$ molal solution of a compound in benzene has a mole fraction of solute equal to 0.2? I tried calculating the moles of $x$ through the value given but there are two ...
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1answer
61 views

Relationship Atmospheric Gases and Ocean Gases [closed]

If this question is better suited for the Earth Science StackExchange or another StackExchange please let me know. Edit 1: Modified for clarity and brevity. Something that's unclear to me is the ...
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26 views

How to calculate the i-value of known NaCl solution, if it is isotonic with known solution of glucose?

How do I calculate the value of $i$ for 1.17% solution of $\ce{NaCl}$, if it is isotonic with 7.2% solution of glucose? I actually do not know where to start in this question. is it possible to ...
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1answer
45 views

Why is a TTT diagram called isothermal transformation diagram?

Why are TTT diagrams called isothermal temperature diagram?As far as I know the temperature variation is plotted with the variation of time in a TTT diagram. Then why do we call it "isothermal".What ...
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47 views

Equilibrium constant when mixing HCl and NaOH

I have 300 ml of a 1 M $\ce{HCl}$ solution and 400 ml of a 1 M $\ce{NaOH}$ solution. These are now mixed at a constant pressure and a temperature of 25 °C. The following neutralization reaction takes ...
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Temperature dependence of reaction rates

Is it correct to say that "Increasing the temperature will always increase the rate of any chemical reaction"? Many articles on the internet and textbooks say yes but what about biochemical reactions ...
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1answer
32 views

How would I find the molarity/concentration of a gas using pV = nRT?

The problem I'm working on is: At $\pu{1100 K}$ and a total pressure of $\pu{1 atm}$, $\ce{SO3}$ is $75.0\%$ dissociated. $$\ce{2SO3(g) <=> 2SO2(g) + O2(g)}$$ Assume $\pu{1.00 mol}$...
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2answers
59 views

Finding the pH of the solution

In this video, at 3:30 min professor solves two equations $$\ce{H2O —> H+ + OH-}$$ and $$ \ce{HCl —> H+ + Cl-}$$ and deduces $[\ce{H+}] = [\ce{Cl-}] +[\ce{OH-}]$. How come this happen from ...
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1answer
43 views

Calculating bond energy given the enthalpy value of burning reaction

The burning enthalpy (exothermic) of $\ce{NO +O2 ->NO2}$ is $\pu{57 kJ mol^-1}$ and $\ce{O=O}$ bond energy is $\ce{494 kJ mol^{-1}}$, then what is the bond energy of $\ce{N-O}$ ? So I balanced the ...
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39 views

Explain why can't zinc be plated out from a Zn(II) solution using standard reduction potentials

I am currently learning about electrochemistry using Zumdahl's Chemistry [1, pp. 709–710]. One of the critical thinking questions is Why can $\ce{Zn}$ not be plated out from an aqueous solution of $...
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18 views

Choosing element with the highest ionization energy [duplicate]

Choose the element with the highest ionization energy: 1. Li 2. Be 3. B 4. N 5. O My answer would be 5. O since its very near to F on the periodic table, hence have more ionization ...
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11 views

In which order should you prepare a microemulsion?

So I have isoooctane (oil phase) ,CTAB (surfactant) ,1-butanol (cosurfactant) , and an aqueous solution of metal nitrates as the water phase. In which order should i add these components? Or any ...
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15 views

How to calculate the internal energy change on a phase change?

Since, the system is in material equilibrium, dG for the system for the reaction is 0. However, our instructor told us that dA has a value. How is that?