# Tag Info

## New answers tagged physical-chemistry

0

Instead of just adding boiling water as @Gert did, lets drain cool water and replace it with boiling. This way we'll keep the total volume of water constant $V=300$ gal. We can determine what volume of water to add $v_\mathrm{add}$. $$(V-v_\mathrm{add})\cdot T_\mathrm{orig} + v_\mathrm{add}\cdot T_\mathrm{add} = V\cdot T_\mathrm{target}$$ $$v_\mathrm{add} ... 2 It's not the question asked, but looking at the power requirements might give some insight. Raising the water temperature requires a specific amount of energy, and the time constraint gives a required power.$$P = \frac{m C T} { t}P = \frac{300\text{gallon }(1000\text{kg/m^3})(4.186\text{J/g K}) 14\text{degF}}{1 \text{hour}}P = ...

1

A typical hot tub will be coming to an equilibrium based on some forcing term $F$ adding heat to the system plus some proportional response $\lambda$ which loses heat to the environment:$$\rho \frac{dT}{dt} = F - \lambda (T - T_0)$$This is a linear ODE whose equilibrium temperature is $T = T_0 + F/\lambda.$ To increase $T$ as fast as possible you should: ...

2

Assuming no heat is lost to the environment the heat balance on adding some boiling water ($212\:\mathrm{F}$) is given by: $$m_{bath}cT_{bath}+m_{added}cT_b=(m_{bath}+m_{added})cT_f$$ where: $m_{bath}=300\:\mathrm{Gall}$ is the initial amount of water, $T_{bath}=32.2\:\mathrm{Celsius}$, $m_{added}$ the amount of boiling water added, ...

0

This is very similar to how plants capture CO2 and form "fuels" (sugars) to feed themselves. In the natural case, the energy comes from sunlight captured by the chlorophylls in the plant cells, and the chemical reaction is carried out by a group of enzymes (Photosystem I and Photosystem II). A lot of scientists are trying to replicate this process ...

0

If light of intensity $I_0$ is incident on a sample or a dielectric interface, at the boundary the following equation will hold: $$I_0 = I_T + I_R + I_A$$ where $I_T$ is the transmitted light, $I_R$ is the reflected light and $I_A$ is the fraction of light which is absorbed by be medium. The absorption is usually calculated from the Beer–Lambert law \phi_T ...

0

Visit http://www.science.uwaterloo.ca/~cchieh/cact/applychem/hydration.html You can see that the enthalpy of hydration is a two step proccess solvation and reverse crystallization, the ΔH(hydr) is actually positive so you have to give energy just to dissolve the NaCl in water, in order to seperate the water from the NaCl you need to account for the enthalpy ...

0

As many comments say, there is not a single and best answer, each one uses a different method. The solution that you found is a good one, but how do you define when the equilibrium has been reached? In order to do that you need check the last values of the simulation (Energy, pressure, etc.), so you choose a set of previous configurations that you'll check: ...

2

Basically “attraction” and “repulsion” are the result of the composed action of some kind of forces. Regarding an atom-atom interaction, even if technically the gravitational attraction exists I assume in this discussion it can be neglected, hence basically you have just the electrostatic interaction as the dominant force. Considering a couple of ...

-2

Atoms have mass, all mass has gravity and everything with gravity attract. Then you have different types of chemical bonds between other atoms. http://dwb4.unl.edu/Chem/CHEM869D/CHEM869DMats/BondTypes.html

2

When you mix water and NaCl together, you create a solution which melting temperature is lower than 0°C (say around -10°C, depending on the amount of salt. When you put salt on a frozen road during winter, the air temperature can be between 0 and -10 degrees, in this case the mixture of ice and salt melts, because the exterior temperature is above the ...

1

When two balls hit each other elastically, energy and momentum are conserved - but they don't usually leave the collision with the same velocity. Each air molecule is like a ball, and at every collision there is a possible distribution of velocities. There is a very small probability that a molecule will be either much faster than all the others, or much ...

0

Okay, this is how I would do it, I would set up cathode and anode to measure the conductivity. I would then compare that to a buffer solution of known ph. If you can't find a buffer solution, see if there is a chart you can find of Hydrogen ion conductivity relationship to pH.(But then you may have to take in temperature of solutions). ...

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