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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Can we do combustion caused by limited supply of air in a lab? How?

For example Ethyne in combustion by limited supply of air 2C2H2 + 3O2 -heat-> 2CO2 + 2H2O + CO2 2C2H2 + 5O2 -heat-> 4CO2 + 2H2O + Energy What are the limits of air availability to make these ...
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48 views

How are nuclei stable?

We all know that the density of the nucleus is very high. Nuclei are made up of protons and neutrons, and while protons have the same charge, they are closely packed in a nucleus. How does the ...
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76 views

Radon gas in earthquake prediction - Why Rn?

I recently studied an article about predicting earthquakes and how correctly realizing that an increase in $\ce{Rn}$ gas is a sign for the earthquake saved a whole city. The following is derived from ...
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20 views

What determines humidity limit / dew point of the air? - Why can air only hold a certain amount of water?

From Wikipedia: The dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At ...
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48 views

Gibbs Free Energy : What is it trying to say actually?

"Gibbs Energy is the useful work that can be extracted from the heat of a rxn or a thermodynamic process." I understand how it predicts the feasibility of a chemical rxn, considering the Entropy ...
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29 views

How to calculate the heat capacity of a calorimeter?

I need to find the heat lost of an unknown metal dropped into a calorimeter with $70~\mathrm{g}$ $\ce{H2O}$. The initial temperature and final temperature of the $70~\mathrm{g}$ $\ce{H2O}$ and the ...
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1answer
22 views

How to calculate the molecular weight for a volatile substance introduced into a Dumas bulb?

In a Dumas bulb a volatile substance is introduced. After a few minutes when the liquid has evaporated, the bulb is sealed. It is known that the initial weight of the bulb with air is ...
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23 views

Comparing the Boiling Points of Two Ionic Compounds [closed]

My question is this: Which has a higher boiling point and why? $\ce{CaCl2}$ or $\ce{FeCl3}$.
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55 views

Is there a pressure dependent function for freezing points of water and carbon dioxide?

I'm trying to determine whether or not certain compounds form solid ice at certain atmospheric pressures. These pressures vary significantly, from 0.001 atm to 800 atm. I understand that there is no ...
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29 views

How is the Rate Law of a reaction measured?

What is Rate Law of the reaction below?$$\ce{4 HBr + O2 -> 2 H2O + 2 Br2}$$ How do we approach finding the rate law of reaction? Can this be found out only through experiments?
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62 views

Why is it obligatory to cool down the container of a sample to measure its mass in a lab?

We were doing an experiment about hydrated crystals and more precisely how to determine $n$ in $\ce{CuSO4.nH2O}$. After we heated the crucible we were to cool it down using a Desiccator. Then this ...
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38 views

Principle of potentiometric titration

In potentiometric titration between Ascorbic acid and Iodine when we plot the graph between EMF with volume of iodine consumed, we get a sudden decrease in emf at equivalance point,Why? It is also ...
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46 views

Any popular experiment in chemistry that digital signal processing played a crucial role in?

Is there any famous experiment in chemistry where digital signal processing played an important part? I don't mean using a machine that relies on such techniques (they all do) but an experiment where ...
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Is it still possible for an amateur, a hobbyist, or a science buff to make relevant discoveries in chemistry today? [closed]

Consider astronomy. Hobbyists and amateurs are today still able to make small to moderate scientific contributions to their field. Is the same true in chemistry? I think there might be at least two ...
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1answer
28 views

Is atmospheric pressure acting only on the contents or also on the container?

$22~\mathrm{g}$ of dry ice is placed in an an empty $600~\mathrm{ml}$ closed vessel at $298~\mathrm{K}$. Find the final pressure inside the vessel, if all $\ce{CO2}$ gets evaporated? Now by ...
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42 views

Prepare 1 liter of 28% NH3(aq) solution from 1 gal of %10 NH3(aq)

I have one gallon of commercial, surfactant free, ammonium hydroxide solution that I would like to use to prepare a concentrated solution. I have two options as I see it, and I am still getting into ...
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1answer
36 views

Is there an isotope effect for diffusion of an ion through a crystal lattice?

Consider the diffusion of natural abundance $\ce{Li^{+}}$ and $\ce{{}^{6}Li^{+}}$ through a crystalline matrix, say a spinel such as $\ce{LiMn2O4}$. The two lithium ions will have the same ionic ...
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67 views

Why does reduced mass help when talking about two body problems?

Firstly I would like to say that despite the fact that you may be thinking that this is a physics question and should probably be asked on that part of the website, I came across reduced mass for the ...
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Looking for a chemical to calibrate a temperature sensor

The best method for calibration would be a bath filled with a chemical at its melting point with a solid/liquid composition. The constraints being that it must be hydrophobic and relatively non ...
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36 views

ph & pOH - Autoionization of Water

So I was learning about pH and pOH and it made sense. I looked at strong, weak acids & bases and learned that they dissociate completely in water. So then I moved on to water and learned about the ...
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63 views

Heat given off from an electrochemical cell compared to mixing reactants

My confusion regarding the difference between the heat given off in a reaction that takes place in an electrochemical cell compared to in a beaker/appropriate container when the reactants are simple ...
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1answer
56 views

Is oil shinier than water? Why?

The physics part: The part that talks about being shiny, I agree, is mainly physics. But proceed in my question, and you'll see how it's a chemistry one. We know things are shiny if they either ...
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39 views

Why does the Born equation give the Gibbs free energy of solvation rather than enthalpy of solvation?

The Born equation gives the difference in energy required to charge a particle in a vacuum and in solution which results in the work required to transfer an ion from a vacuum into solution. It is ...
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36 views

What happens to energy changes in non-reversible processes?

Take internal energy for example: $$dU\leq TdS-PdV$$ Firstly, I would like to make clear that the following question/argument relies on the following statement being correct: the left hand side of the ...
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58 views

For a system to undergo a spontaneous change at constant temperature and pressure the Gibbs free energy must decrease, but how?

$$dG<VdP-SdT$$ So for a process at a constant pressure and temperature, and in the absence of any non-pV work, $dG<0$. Since energy cannot be created or destroyed (and Gibbs free energy is a ...
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Are the values for enthalpy, internal energy and Gibbs free energy the same for a particular process?

Internal energy, enthalpy and Gibbs free energy are all units of energy. So, for any particular process where energy is lost from the system the same amount is given off to the surroundings. Am I ...
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345 views

Whats the difference between entropy and the (dis)order of a system?

Entropy is often verbally described as the order/disorder of the thermodynamic system. However, I've been told that this description is a vague "hand-waving" attempt at describing what entropy is. For ...
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68 views

Beta Decay - Doesn't Add Up [duplicate]

The definition of Beta Decays is as follows Electron comes out. Example as follows: $$\ce{^131_53I -> ^131_54Xe + e^-}$$ So Iodine forms Xe and releases one electron with a -1 charge only and ...
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68 views

Chemical or Physical? I Think Physical

So I came across this question asking whether something is physical or chemical. Table Salt is Composed of $\ce{Na}$ & $\ce{Cl}$. Is it a physical property or a chemical property? I really ...
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How does the chemical potential allow for open systems to be considered?

Gibbs free energy can be defined as: $$dG=VdP-SdT+\sum_i\mu_idn_i$$ where $\mu=(\frac{\partial G}{\partial n})_{P,T}$. Last term, $\sum_i\mu_idn_i$ allows for open systems to be considered (where $dn$ ...
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40 views

Gibbs free energy can be expressed as a function of P,T and n but are enthalpy and internal energy also (partially) functions of n?

$$G=G(P,T,n)$$ $$dG=VdP-SdT+\mu dn=(\frac{\partial G}{\partial P})_{T,n}dP+(\frac{\partial G}{\partial T})_{P,n}dT+(\frac{\partial G}{\partial n})_{T,P}dn$$ This allows open systems to be considered ...
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If the standard state symbol means that the substance is pure (and at 1 bar) how is it possible to have a standard REACTION enthalpy?

For the reaction one mole of substance $A$ in equilibrium with one mole of substance $B$ the standard reaction enthalpy is defined: $$\triangle_rH^{\theta}(T)=H_m^{\theta}(B;T)-H_m^{\theta}(A;T)$$ ...
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39 views

How to accurately calculate the electromotive force for various conditions in a salt water battery?

This question is on the same topic as this one but more complex. So, let's consider the cell with $\ce{Zn}$ and $\ce{Cu}$ electrodes inside the $\ce{NaCl}$ solution. On the $\ce{Zn}$ electrode we ...
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34 views

Chemical Composition Changes in Liquids

Water is $\ce{H2O}$ in all it's states: solid(ice), liquid, and gas(water vapor). In your drink, when you add artificial flavoring and coloring, does it change the chemical composition of the water? ...
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Why is dG=dH-TdS?

I get that $G=H-TS$ because then: $dG=dH-TdS-SdT=TdS+VdP-TdS-SdT$. Therefore, by cancelling: $dG=VdP-SdT$ which is the equations for dG. However, I cant get this result from using $dG=dH-TdS$. ...
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34 views

Problem with proving that entropy is a state function

$$dU=dq-pdV$$ $$dU=C_VdT$$ Side question: is the above equation, $dU=C_VdT$ true only for a perfect gas or all substances? $$C_VdT=dq-pdV$$ $$dq=C_VdT+pdV$$ Divide by T $$dS=\frac{C_V}{T}dT+\frac ...
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Thermodynamic micellization of potassium N-dodecanoyl-DL-serinate via conductivitiy measurements

I have a set of data and my instructor asked me to calculate some parameters but I am not good in maths. I will give you for data potassium N-dodecanoyl-DL-serinate (DL-KDDS); K: Conductivity C: ...
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Why is Gibbs free energy more useful than internal energy?

$$\mathrm{d}U<T\,\mathrm{d}S-p\,\mathrm{d}V= \left(\frac{\partial U}{\partial S}\right)_{\!V}\,\mathrm{d}S +\left(\frac{\partial U}{\partial V}\right)_{\!S}\,\mathrm{d}V$$ So for a change to occur ...
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22 views

Can a change in internal energy always be expressed as the product of the constant volume heat capacity and the change in temperature?

It makes sense to me conceptually that $dU=C_VdT$ but is that always the case because I have seen that result derived thus: $$dU=U(V,T)=(\frac{\partial U}{\partial T})_VdT+(\frac{\partial U}{\partial ...
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1answer
51 views

Calculating the Gibbs Free Energy of Mixing

This is a Physical Chemistry Question and comes from the Atkins Physical Chemistry book. The answers are given but I don't understand how to get to $-9.7~\mathrm{kJ}$ for the first part of the ...
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2answers
27 views

Expressions for constant volume and constant pressure heat capacities

My lecture handout says: $$C_V=\frac{dq_V}{dT}=(\frac{\partial U}{\partial T})_V$$ I understand that $C_V=\frac{dq_V}{dT}$ and that $dU=dq_V$ but what's the need for the partial derivative. Why can ...
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150 views

Why is the units of kcat 1/s?

I understand that $k_\text{cat}$ measures the turnover number of an enzyme. This measure is therefore a quantity of molecule conversions per unit of time. I suspect that my problem is more that of a ...
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What causes the lowering of vapour pressure in volatile/nonvolatile solvent mixtures?

"Based on Figure 13.18, you might think that the reason volatile solvent molecules in a solution are less likely to escape to the gas phase, compared to the pure solvent, is that the solute molecules ...
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21 views

What are the possible concentration pathways for a 3-species system?

Inspired by this question, which asks if a multi-species system could oscillate around its equilibrium, I thought about the possible concentration pathways the following more narrow specified system ...
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51 views

Which formula is correct for calculating the heat of dissolution?

I want to calculate the energy change when a solute is dissolved in water. I know that I can achieve this by using the equation $q=mc \Delta T$. My question is does the mass ($m$) change with the ...
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1answer
56 views

How to find and use the Clausius-Clapeyron equation

I know how to get the equation from the Clapeyron equation but I have a question regarding a the integration along a phase boundary and a small step in the derivation that I will make clear when I ...
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40 views

Why is activation enthalpy found and not just rate of reaction?

What is the benefit of finding activation enthalpy and not rate of reaction?
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27 views

In a mass spectrum, how can the sum of relative abundances be greater than 100?

I apologise if this seems a very simple question, and also if I am overlooking something that is very simple. For part of my A Level course, we have to be able to interpret mass spectrometer readings ...
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85 views

How was the diatomic nature of many common gaseous elements originally determined?

How did scientists find out that $\ce{Cl2, H2, O2}$ atoms have a two-atomic molecular structure ?
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Is it likely that increased understanding of quantum physics will change our understanding of chemistry?

Reading that the large hadron collider will be up and running with twice as much energy in March 2015, I was curious whether our understanding of subatomic particles has changed our understanding of ...