Questions tagged [temperature]
A measure of the average kinetic energy of the particles in a sample of matter; may be expressed either in kelvin (symbol K) or in degree Celsius (symbol °C).
412 questions
1
vote
0
answers
29
views
Temperature of thermal dissociation of carbon monoxide?
I was reading a paper about CO2 splitting, which mentions limitations of high temperature approach:
NTP even in the presence of solid catalysts is not able itself to
effectively promote the CO2 to C +...
- 21
2
votes
0
answers
60
views
What is the correct way to approximate the diffusion rate of gases in water as a function of temperature?
In applied chemistry/physics, I see the diffusion coefficient of gases in water being approximated by various ways.
Arah and Stephen 1998 for instance use a linear Dw(T) with 0 intercept for methane ...
- 21
0
votes
1
answer
61
views
Molar Concentration as a Function of Mole Fraction
I am using the ideal gas law for a gas mixture and would like to confirm the following derivation and simplification.
Starting from the ideal gas law:
$$\rho = \frac{P \cdot M}{R \cdot T}$$
where:
$\...
13
votes
7
answers
2k
views
Do some chemicals degrade at low temperatures?
I was reading an article on how medicines degrade over time and how that could be a problem on a trip to Mars.
Which got me thinking. Surely the obvious solution is to store them at low temperatures. ...
- 1,836
1
vote
0
answers
44
views
Why would large activation energies give a large gradient of the rate constant?
I have read carefully this answer on SE, and there is a part I don't understand. SE exchange user said:
If you plot the Arrhenius equation (given in your text) vs temperature the slope of this gives ...
- 267
2
votes
1
answer
69
views
Temperature compensation when measuring pH and how to calibrate
We want to measure the pH of liquid solutions (impure water) with a sensor that returns a voltage (by measuring the difference of potential inside and outside a glass bulb). The manufacturer provided ...
- 21
1
vote
1
answer
80
views
How to derive absolute temperature scale from Carnot engine?
This question is about how to obtain an absolute or thermodynamic temperature scale using a Carnot engine.
The reasoning below appears in the book "Heat and Thermodynamics" by Zemansky and ...
- 178
0
votes
2
answers
113
views
Finding the point where reaction switches from endothermic to exothermic
One mole of monoatomic gas undergoes a linear process A to B shown in P-V diagram. Volume of gas from where process turn from an endothermic to an exothermic is?
I tried to calculate the point where ...
- 23
0
votes
0
answers
20
views
Why is water the densest at 277K? [duplicate]
From what I have seen/heard of, all the elements get denser and denser the cooler its temperature is; but for water, it isn't like that. After 277K, the water expands. Why is this? Is it because the ...
4
votes
0
answers
90
views
Maxwell Boltzmann Curve two peaks
In the image, the second peak appears lower and more plateau-like. What is the chemical reasoning behind this phenomenon? While I understand the relationship between temperature and peak height (with ...
user145852
10
votes
5
answers
4k
views
Why don't room temperature superconductors exist?
It seems like high-temperature and low-temperature superconductors are not too rare. But, why don't any superconductors work at room temperature? No theories seem to predict their occurrence, but none ...
user145708
-2
votes
2
answers
94
views
Surface Tension at Critical Temperature and at Boiling point [closed]
I recently did an experiment on finding the surface tension of a liquid at different temperatures, When I was going through my lab manual, I found the following statement:
As temperature decreases, ...
- 382
2
votes
1
answer
264
views
Distillation thermometer position
I am aware that in theory the position of the thermometer needs to be right at the transition point of the vapor into the condenser. In practice,I don´t reach the exact boiling temp. at this height ...
- 89
1
vote
0
answers
126
views
Why is the standard enthalpy of formation temperature-dependent in JANAF tables?
I'm unsure why $\Delta_\mathrm{f}H^\circ$ within the NIST-JANAF Thermochemical Tables [1] is temperature-dependent. Wouldn't the $\Delta_\mathrm{f}H^\circ$ represent the enthalpy of formation at the ...
- 111
0
votes
4
answers
468
views
Storage of air and temperature sensitive reagents [closed]
What's your method for storing air/moisture and temperature sensitive reagents? For example:
A solid. Should I just blow some argon, screw the lid, put parafilm and put it in the fridge? Can a ...
user78790
1
vote
2
answers
329
views
How exactly does the Nernst equation account for temperature? [duplicate]
I am doing an experiment that involves changing the temperature of the electrolytes in a voltaic cell and seeing the effect on the initial voltage produced. I'm a bit confused because if I use the ...
- 11
-4
votes
1
answer
79
views
Is the liquid in this question water? How can one know for sure? [closed]
I have been studying and there is a question in my book asking:
A faulty thermometer reads freezing and boiling point of a liquid as -5°C and 95°C respectively on the Celsius scale. What is the ...
- 103
0
votes
1
answer
68
views
Temperature and electrolysis
Based on my understanding, metals conduct electricity better at lower temperatures than at higher temperatures as the resistance to electron flow is lower.
Then, what about ionic compounds? Do they ...
1
vote
1
answer
38
views
Is vibronically resolved spontaneous emission temperature dependent, following a distribution defined by the canonical density operator?
Does the lifetime of a molecular excited electronic state, for example the $S_1$ state, suffice for thermal equilibration before spontaneous emission occurs?
For example the fluorescence of coumarine, ...
- 1,300
0
votes
1
answer
182
views
At what temperature is bismuth the densest?
Both water and bismuth have denser liquids compared to solid forms, and we know water is the densest at the temperature of about 4°C.
Does the same thing apply to bismuth? Of course, I know the ...
user85778
-1
votes
1
answer
102
views
Highest possible temperature [duplicate]
I know the lowest possible temperature in nature is 0 K although we have been able to only getting ever closer and closer to it but not at 0 K.
But on the opposite spectrum of temperature, what is the ...
- 752
1
vote
0
answers
78
views
Total bond dissociation temperature [closed]
I understand that covalent bonds break at a dissociation energy $D_0$ that is a function of the particular bond. And it looks like an upper bound on $D_0$ is known for possible covalent bonds.
It's ...
- 3,352
-4
votes
1
answer
820
views
According to PV=nRT,if we increase temp,no of moles will decrease,but no of moles is dependent on mass,mass is constant,then how can moles change?
We know the ideal gas equation is PV=nRT,then, according to this,if we keep Pressure,volume to be constant,then on increasing temperature,no of moles will reduce,this would mean that mass of matter or ...
- 3
-1
votes
2
answers
292
views
At what temperature is ammonia liquid at 1.5 bars? [closed]
I would like to know at what temperature ammonia condenses from gaseous form into a liquid, at a pressure of 1.5 bars. I know that at normal 1 bar pressure, ammonia is a liquid between -78 and -33 ...
0
votes
2
answers
145
views
Can anyone help me with the derivation for the formula of entropy?
I have this formula in the chapter of thermodynamics:
$$\Delta S = n C_v \ln\left(\frac{T_2}{T_1}\right) + n R \ln\left(\frac{V_2}{V_1}\right),$$
where $\Delta S$ is entropy, $n$ moles, $C_v$ molar ...
- 11
0
votes
1
answer
44
views
What happens to the air pressure above water as its heated to and past boiling?
If I put a pressure sensor inside an airtight container half-filled with water, and heat the water, what will the pressure sensor read as the temperature increases? Would it linearly increase (black ...
- 183
-2
votes
1
answer
760
views
When does Van't Hoff's reaction rate rule not work?
I have a problem answering a question in my lab report.
The question is about the empirical van't Hoff's rule - what does it say and what are its limitations?
I managed to find online that the ...
2
votes
1
answer
55
views
Is it easier to produce hydrodynamic cavitation in a liquid close to boiling point?
Cavitation is defined as the process of formation of the vapor phase of a liquid when it is subjected to reduced pressures at constant ambient temperature. Thus, it is the process of boiling in a ...
- 183
-1
votes
5
answers
265
views
Why aren't the units for temperature related to kinetic energy, if temperature is defined as average kinetic energy?
Temperature, as far as I know, is a measure of the average kinetic energy of the particles in a substance. For instance, if a bar of pure gold is sitting at room temperature ($273.15 \text{ K}$), then ...
- 279
-1
votes
1
answer
210
views
Is there any chemical that can react with two different chemicals to generate heat or cold? [closed]
For example. There are three chemicals. Chemical A,B,C
Chemical B react with Chemical A = heat
Chemical B react with Chemical C = cold
Is there any chemical available like this? And is it safe to ...
- 7
-4
votes
1
answer
303
views
How it was decided that the freezing point of water in the Kelvin scale of temperature should be 273.15 K? [closed]
While discussing about the different temperature scales, our teacher told us about the freezing point and boiling point of water in different scales. I asked my teacher that how these numbers were ...
- 13
1
vote
2
answers
5k
views
What is the entropy change in isochoric process
I have studied that entropy increases with increase in temperature and it decreases with increase in pressure but in case of isochoric process both are happening at the same time but still the overall ...
- 29
0
votes
1
answer
1k
views
I tested the effect of temperature on the pH of carbonated water but the results seem to go opposite to what was expected. Could anyone explain?
We carried out an experiment to investigate the effect of temperature on the acid carbonate equilibrium in carbonated water. We tested 5 different temperatures (room temp, 2 above and 2 below) by ...
0
votes
0
answers
60
views
If liquids absorb heat from their surroundings to become gas, why does gas feel hotter than liquid?
I know what you're thinking, "OP, are you for real!? Gas is obviously hotter because it absorbed heat from the environment!"
But hear me out. Yes it is hotter in absolute terms because it ...
- 1
0
votes
2
answers
1k
views
Why does temperature remain constant during phase changes?
In a phase change the temperature remains constant but I can't understand why. The answers I have read state that during phase changes energy is only used to break bonds between molecules rather than ...
- 221
10
votes
1
answer
430
views
In a liquid-in-glass thermometer, how does the gas pressure over the liquid affect the linearity of measurement?
In a common ethanol thermometer, the space above the alcohol column is filled with nitrogen. It also contains varying amounts of the alcohol in the gas phase.
Source: http://www.aashtoresource.org/...
- 42.3k
-4
votes
1
answer
74
views
What happened after fire finished burning? [closed]
After fire finished burning, did it merge with the atmosphere and becoming water vapors, oxygen and nitrogen, or did it simply disappear into nothing?
- 101
-1
votes
1
answer
307
views
Can we calculate final temperature of two gases in thermal contact? [closed]
This is a question from IIT-JEE - ADVANCE 2018
A closed tank has two compartments A and B, both filled with oxygen (assumed to be ideal gas). The partition separating the two compartments is fixed ...
- 23
0
votes
1
answer
157
views
Pressure and temperature relation of Novec 1230
I am working on a concept turbine for a school project which operates at low temperature so it's necessary for me to have a pressure temperature relation of this chemical or novec 7100 also is okay.. ...
0
votes
0
answers
38
views
How do I calculate the temperature change in a gaseous reaction?
So, with $\pu{3 mol}$ of $\ce{H2}$ and $\pu{3 mol}$ of $\ce{Cl2}$ and given the reaction $\ce{H2(g) + Cl2(g) -> 2 HCl(g)}$ with $\Delta H=\pu{-184.6 kJ/mol}$, I am supposed to calculate the work ...
6
votes
1
answer
262
views
Water getting hotter once frozen?
I packed a fridge with temperature sensors and took over the temperature control in order to have extra cold beer.
One of those sensors is submerged in the middle of a container containing a 4.5% ...
- 171
0
votes
0
answers
39
views
Is the relation [K] = [C] + 273.15 exact? [duplicate]
In reading Atkins' Physical Chemistry, the first section of the first Chapter, the author says that the conversion equation between the absolute temperature and celsius is exact and at the same time ...
- 109
1
vote
0
answers
293
views
What polyatomic substances have the lowest known freezing points at standard pressure?
At standard pressure, helium never freezes, so that's clearly the coldest liquid—but it's also a monatomic substance.
Diatomic hydrogen freezes at 13 K.
Neon freezes at 24 K.
And then the next coldest ...
3
votes
2
answers
230
views
What does the heat capacity really represent? [closed]
According to Wikipedia, heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature:$$C = \...
- 332
3
votes
2
answers
989
views
Stratification of gasses by mass [closed]
Suppose a homogenous mixture of mutually non-reactive gases is isolated in a container so that there are no external kinetic forces (vibration or rotation) that create turbulence or other mixing ...
- 3,352
0
votes
1
answer
422
views
If I heat a solution to bring a solute in solution, will it precipitate when it goes back to room temperature?
Suppose I'd like to bring a solute into solution at a concentration above its solubility at $\pu{25 ^\circ C}$, so I heat the solution and achieve a concentration above the $\pu{25 ^\circ C}$ ...
1
vote
0
answers
722
views
How does the temperature of HCl affect the reaction rate of HCl & Mg reaction?
I'm Olivia. I'm experimenting with HCl and Mg. My purpose is to find the change of the reaction rate while I increase the temperature of HCi.
According to the study, when I increase the temperature of ...
- 11
0
votes
1
answer
294
views
What would happen to the cell potential if two half cells of a galvanic cell were at different temperatures?
I'm doing an experiment where I'm investigating the effect of temperature of the galvanic cell on the cell potential. But during the experiment, I noticed that the two half cells were at different ...
- 1
0
votes
1
answer
4k
views
How do I calculate the maximum temperature of an exothermic NaOH reaction in water?
As the title suggests, let's say I want to make a 1 L 14M NaOH solution. For this I'd need:
(14 mol/ L) x 1 L x (39.99 g / mol ) = 559.86 g NaOH(s) {solute}
~1 L H2O (approx) {solvent}
The ...
- 500
0
votes
1
answer
1k
views
Why does temperature increase rate of electrolysis even though resistivity of electrodes increase?
My experiment is just the electrolysis of iron rust at different temperatures. It consists of a rusted iron cathode and an iron anode in a salt water solution. From my data, there is an approximately ...
- 27