Thermochemistry Definition and 82 Threads

I am trying to understand how certain endothermic reactions work as a layman. I found the idea of reducing a rock to separate atoms fascinating, like what you would see in a comic book. However, I struggled to wrap my head around what that process would be like. I did some preliminary research...

Greetings. This is my first post here. I hope I can get some assistance for my problem. Context Just to preface, this is just for a hobby and not any kind of homework or professional problem. With that said, I have been writing calculation step-by-step guides on phase changes in an effort to...

I really struggled with this problem and did not make headway on my own. Here is the solution from the solution manual. I tried to understand the above by drawing the following picture. Reaction 1 is the balanced equation for the reaction that happened in the constant-volume calorimeter...

We can compute the enthalpy of reaction of ##\mathrm{O_2(g)\rightarrow 2O(g)}## at 0K by heating reactant to 298.15K, doing the reaction and obtaining the product at this temperature, and then cooling the product down to 0K. The result is $$\Delta H_r=\mathrm{493.48kJ\ mol^{-1}}$$ According...

The above question is the final part of a problem in Silbey, Alberty, and Bawendi's Physical Chemistry. The main part of the problem had to do with various calculations of changes in enthalpy at 500K, which I completed successfully. The single reaction is endothermic with reaction enthalpy...

This is a problem from the book "Physical Chemistry" by Silbey, Alberty, and Bawendi. The end of the book says the answer is ##41.572\text{kJ/mol}##. Here is how to obtain this answer There is a table a the end of the book with the following entry The fourth column is...

The combustion reaction for 1 mol of propane is $$\mathrm{C_3H_8(g)+5O_2(g)+20N_2(g)\rightarrow 3CO_2(g)+4H_20(g)+20N_2}\tag{1}$$ and by using the given enthalpies of formation we can easily compute $$\Delta_{rxn} H^\circ=-2043.73\text{kJ}$$ This enthalpy of reaction is for an isothermal...

Good evening, unfortunately I'm pretty lost in this problem. I tried to use the chain rule $$(\frac {\partial H} {\partial v})_P = (\frac {\partial H} {\partial T})_P (\frac {\partial T} {\partial v})_P$$ and using some Maxwell relations but it doesn't work very well. I know that $$T = (\frac...

SO2(g)+1/2O2(g)⇌SO3(g);ΔHo=-98.32KJ/mole,ΔSo=-95J/(mole-K). find Kp at 298 Kelvin? In given question at first Δ G will be calculated using formula ΔG = Δ H – T x ΔS, by putting the given values in formula we get ΔG = -70.01 kJ/mol. Then Keq will be calculated using equation = Δ G = -RT ln Keq...

I was reading about thermodynamics postulates when i came over the differnetial fundamental equation: I understand that the second element is just pressure and last element is chemical energy, but he problem is i don't understand what is the use of entropy and how does it contribute to a...

Hi all! I was wondering, Is it possible, given a specific dipolar molecule, to create the perfect oscillating electric field so as to heat it and not, i.e. the water around it? What I'm basically asking is could there exist a specific microwave just for X and not all dipolar molecules without...

In chemical reactions generally ΔG < 0 , but if we were to consider a reversible path between pure reactants and products at 1 bar pressure , shouldn't the ΔG = 0 for every reaction ? and if it is due to non-pv work , I don't see any non pv work being done in reactions happing in a closed...

Summary:: TLDR : Drink cooled from 17 C to 7 C with either ice cubes (method 1) or soapstone stones (method 2). Calculate the mass of each item that would be needed to cool the same drink. Given the information provided. In order to cool a drink (“cola” for example) from a storage-room...

Can anyone explain how is this reaction ? I 've evaluated the moles of CO and N2 but now i can't see how is this reaction written CO + N2 ...?

The balanced reaction wil be : ##2C_6H_{6(l)}+15O_{2(g)}->12CO_{2(g)}+6H_2O_(l)## in order to compute the the standard enthalpy of reaction : ##\Delta H°_{f} H_2O_(l)= -285,8 \frac {KJ}{mol}##; ##\Delta H°_{f} CO_{2(g)}= -393,5 \frac {KJ}{mol}##; ##\Delta H°_{f} C_6H_{6(l)}=49,04 \frac...

Hi Folks, I have been trying to find data on the enthalpy of combustion of acetylene and fluorine. I have found the data for oxygen but am curious about the use of pure fluorine in stochiometric conditions and the resulting upper heating value when the oxidant is acetylene. I am happy to...

My book introduces Thermochemistry with the concept of heat and how a calorimeter works. After that, it explains the story behind Hess Law and says that one of the reasons it was created is because a calorimeter can't calculate fast chemical reactions, but it doesn't really say the problem with...

Homework Statement For the reaction below, the constant pressure heat of reaction is qp = −3256 kJ mol−1 at 25 °C. What is the constant volume heat of reaction, qV , at 25 °C? 16 CO(g) + 33 H2(g) ⟶ C16H34(l) + 16 H2O(l) Enter your answer in kJ mol−1, rounded to the nearest kilojoule...

1. Homework Statement What are the values of q, w, ΔU, ΔH for the following constant pressure process for a system containing 0.596 moles of CH3OH ? CH3OH(g, 123.0 ºC, 1.00 atm) ⟶ CH3OH(l, 30.0 ºC, 1.00 atm)Molar heat capacity for CH3OH(g), Cp,m = 44.1 J K−1 mol−1 Molar heat capacity for...

Homework Statement What is w when a gas is compressed from 42.1 L to 25.1 L using a constant external pressure of 739 Torr? Remember to include a "+" or "−" sign as appropriate. Homework Equations W = -P(dV) The Attempt at a Solution Pressure = (739 Torr / 760 Torr)*(101.325 kPa) W =...

Homework Statement The enthalpy of neutralization for the reaction of a strong acid with a strong base is -56 kJ/mol of water produced. How much energy will be released when 195.0 mL of 0.400 M HCl is mixed with 155.5 mL of 0.500 M NaOH? Homework Equations c=n/V The Attempt at a Solution to...

Homework Statement Consider the following reaction. 2 HCl(aq) + Ba(OH)2(aq) BaCl2(aq) + 2 H2O(l) ΔH = -118 kJ Calculate the heat when 100.8 mL of 0.500 M HCl is mixed with 300.0 mL of 0.450 M Ba(OH)2. Assuming that the temperature of both solutions was initially 25.0°C and that the final...

Homework Statement Consider the dissolution of CaCl2. CaCl2(s) Ca2+(aq) + 2 Cl-(aq) ΔH = -81.5 kJ A 10.6-g sample of CaCl2 is dissolved in 109 g of water, with both substances at 25.0°C. Calculate the final temperature of the solution assuming no heat lost to the surroundings and assuming...

Homework Statement area=2.25 p1=1bar v1=0.23m3 p2= v2=1m3 Homework Equations Isothermal process W=nrt ln(v2/v1) W=F*D The Attempt at a Solution I got the workdone then sub into the equation of isothermal process. i couldn't get the answer right

Homework Statement Estimate the average S-F bond energy in SF6 The standard heat of formation values of SF6(g) , S(g) and F)(g) are: -1100, 275 and 80 kj / mol respectively. Homework Equations ∆H=∆Hf (products) -∆Hf(Reactants) S(g) +6F)(g) ------>SF6(g) The Attempt at a Solution I...

Looking through the book of abstracts for «XXI International Conference on Chemical Thermodynamics in Russia (RCCT-2017)» I came across the abstract of talk given by Peter Atkins (University of Oxford) titled «Thoughts about thermodynamics» (you'll find the whole abstract at the end of the...

Homework Statement Here is the original question (just read the English version). Homework Equations Q = mcθ Specific heat capacity of water, c = 4200 J/kg °C The Attempt at a Solution I did Q_(absorbed) = Q_(released) mcθ = mcθ mθ = mθ And I solved for the final temperature, which is...

Homework Statement Show that to a first approximation the equation of state of a gas that dimerizes to a small extent is given by, ##\dfrac{PV}{RT} = 1 - \dfrac{K_c}{V}## Where ##K_c## is equilibrium constant for ##A + A \iff A_2## Homework EquationsThe Attempt at a Solution Using virial...

Homework Statement Use the van der waals constant for ##H_2## and ##O_2## to calculate the initial slopes of the plots of compressibility factor Z versus P. Homework EquationsThe Attempt at a Solution Using virial expansion for van der waal gas in terms of ##P## I get ##Z = 1 +...

For example: If I isolated (in a perfect vacuum), one Magnesium atom and one Oxygen atom, and they are close to each other, will they make a bond by themselves, with no outside energy? Does this work with any combinable pair of atoms, and what other pairs of atoms would make a bond by...

I have a reversible chemical reaction described by the balanced equation: ##aA+bB=cC+dD##. I devise a reversible process to take a closed system containing these species (and its surroundings) from thermodynamic equilibrium state 1 to thermodynamic equilibrium state 2: State 1: a moles of...

I'm a first year electrical engineering student and in my General Chemistry class, every other week, we're required to write a paragraph about how each weeks material relates to your future career. As I am in electrical engineering, I don't see much relation to any topic. This week is...

Homework Statement Freezing of water at 273 K and 1 atm which of the following is true for the above thermodynamics process p) q=0 q)w=0 r)ΔSsys<0 s)ΔU=0 t)ΔG=0 Homework Equations none[/B]The Attempt at a Solution [/B] i got r, s ,t since the reaction happens at constant...

Ok, this is a large qiestion. Firstly, from second law of thermodynamics, thermal flow always happens between matters kept in different temparature. But while an endothermic reaction takes place, it may extract some heat from environment and consume it. Isnt it against second law? And for...

I want a book on Thermo and statistical physics that will give me a clear insight on every basic thermodynamics systems. I am already done with Shroedar's introduction to thermal physics btw. I basically need a book that clears my concept more than solving problems. And the more on...

Homework Statement Calculate ∆rH° for the reaction c2h50h+3o2-->2co2+3h20 Given that ∆rU° = - 1373 kJ mol-1 at 298K. Homework Equations c2h50h+3o2-->2co2+3h20 The Attempt at a Solution delta H f CO2(g) = -393.5 kJ/mole delta H f H2O(l) = -241.8 kJ delta H f O2(g) = 0 these values are...

Why does ∆S = 0 for a reversible process, but for a reversible isothermal process, ∆S is given by nRln(Vf/Vi) (or other variations of that equation)?

Homework Statement A sample consisting of one mole of a diatomic perfect gas is heated from 25 °C to 200 °C at constant volume. Calculate q, w, ΔU and ΔH for the process, given that Cv = 23.02 J K-1 mol-1 . Homework Equations Im studying for mid terms and i have no lecture notes on diatomic...

Homework Statement An ice cube melts in a 10oC glass of water (mass of water is 225g). If the ice is allowed to melt completely, what will the final temperature of the water be? (we're told that the mass of ice can be ignored) Ti = 10oC Latent heat of fusion = Lf = 334000 J/kg specific heat...

Homework Statement You have 0.50 mol of steam which has been supercooled to 95˚C at 1 atm. Since the steam is below the boiling/condensation point, it proceeds to partially condense into liquid water. This happens in a thermally-insulated vessel at constant pressure. (a) When the system...

Hi I have a few questions that I have been working on but I don't get the right answer. After drawing the Lewis dot structure of HOClO2, pick the incorrect statement of the following. A. The oxygen bonded to the hydrogen has two lone pairs B. the oxygens not bonded to hydrogen have three lone...

Homework Statement Adsorption, coagulation, and flocculation are all important processes to remove or separate target substances from mixtures. In these processes, we can observe the spontaneous decrease of entropy.; can we therefore conclude that the second law of thermodynamics doesn't always...

Homework Statement Why does ##\Delta H=\pm |q_{surroundings}|##? Homework EquationsThe Attempt at a Solution Exothermic reactions have a ##-\Delta H## but does that mean that ##q## is a ##+q##. Vice versa for a endothermic reaction. I get confused on which sign i should use for which when i do...

Hello PF! I have a very short question. We're currently doing enthalpy balances for chemical reactions in our Thermo class. We are using the simple enthalpy balance equation: \Delta H_{\textrm{Reaction}}^0 = \sum \Delta H_{\textrm{Products}}^0 - \sum \Delta H_{\textrm{Reactants}}^0 My question...

Homework Statement If 13.4 kJ of heat is added 1.00 kg of ice at 0ºC, how much ice will be melted Homework Equations Change of Heat = mass*change of temperature*constant change of heat fusion (water) = 333 J/g change of heat water vapor = 2260 J/g change of heat total = change of heat...

Which books can anyone recommend with the most comprehensive or fundamental coverage of chemical thermodynamics and thermochemistry, linking up to equilibrium (including electrochemical equilibrium and potentials preferably), starting from the basics? I find the explanations of the topics of...

Homework Statement A block of copper at 100.0° C comes into contact with a block of aluminum at 20.0°C. The final temperature of the blocks is 60.0°C. What are the relative masses of the blocks? Homework Equations mcΔT copper specific heat = .386 J/g°C aluminum specific heat = .900...

Hello, I am currently studying intro to thermochemistry. I noticed in some problem solutions the equation q=mc(Tf-Ti) but in other the equation is q=c(Tf-Ti). How come sometimes the mass is not used in the equation? When do you know which one to use? Thanks!

Thermochemistry significance of "infinitely dilute solution" Homework Statement (see attachment) Homework Equations The Attempt at a Solution I don't know where to start from and it seems to me that data given is insufficient to solve this problem. Also, what's the significance...