Laplace number: Difference between revisions

From formulasearchengine
Jump to navigation Jump to search
← Older edit
en>Rememberlands
m roman dimensionless numbers
en>Wizardman
m clean up using AWB
 
Line 1: Line 1:
The '''standard enthalpy of reaction''' (denoted Δ<sub>r</sub>''H''<sup>⊖</sup>) is the [[enthalpy]] change that occurs in a system when one mole of matter is transformed by a [[chemical reaction]] under [[standard conditions]].
Most bars, nightclubs and restaurants have epoxy bar tops.  If you cherished this report and you would like to get far more details with regards to [http://www.43things.com/entries/view/6499747 resinas epoxi] kindly pay a visit to the web site. It is shiny, clear, thick surface, sometimes with some objects inside. Coins, cards and other small item you seen inside clear resin.<br><br>What material do they use to build those bar tops and what the process?<br><br>Most of the time it is 2 parts chemicals mixed with 1:1 ration. The process is complicated and done by professionals only. Part #1 is epoxy resin and the part #2 is hardener. There are different types of epoxy, based on what you want to accomplish.<br><br>Table top resin - main purpose is for table tops, bar tops and any other horizontal surfaces with perfect flat finish. Casting resin/epoxy - used to make molds or building up thickness. If used correctly, may have perfect final surface. Spray Epoxy - this epoxy you can place in spray gun and apply like a lacquer. Sprays in thin layers and grabs pretty quick.<br><br>Have you ever seen someone working with epoxy - it is very interesting process.<br><br>Area around the bar gets covered with protective film to prevent any spills to get on the floor.<br><br>Surfaces get wiped several times with different liquids to completely remove any fat deposits from fingerprints to prevent "fish eye". Process of poring resin on the bar top normally done in several layers. So if you want to place small objects inside epoxy/resin bar top - you can do it between coats.<br><br>Resin bar tops are very durable. Surface is hard to scratch and easy to clean. If done correctly it will serve you for 10 years and more.<br><br>Can you do it yourself, yes. It is absolutely important to find epoxy supplier who not only work with epoxy but also willing to give you directions on how to work with product and willing to guide you through the process.
 
For a generic chemical reaction
 
:−''v''<sub>A</sub> A + −''v''<sub>B</sub> B + ... → ''v''<sub>P</sub> P + ''v''<sub>Q</sub> Q ...
 
the standard enthalpy of reaction Δ''H''<sub>r</sub><sup>⊖</sup> is related to the [[standard enthalpy of formation]] Δ''H''<sub>f</sub><sup>o</sup> of the reactants and products by the following equation:
 
<math>
\Delta H_\mathrm{r}^\ominus = \sum_{B}{v_B\Delta H_\mathrm{f}^\ominus(B)}
</math>
 
In this equation, ''v<sub>B</sub>'' is the [[stoichiometric number]] of entity B.
 
A similar enthalpy change is the [[standard enthalpy of formation]], which has been determined for a vast number of substances. The enthalpy change of any reaction under any conditions can be computed, given the standard enthalpy of formation of the reactants and [[Product (chemistry)|product]]s.
 
It is defined as the amount of heat absorbed or evolved in the transformation of the reactants at a given temperature and pressure into the products at the same temperature and pressure.
Enthalpy of a reaction at constant pressure and at a constant volume:
Enthalpy of a reaction depends upon the conditions under which the reaction is carried out. There are two general conditions under which Thermochemical measurements are made.
 
(a) Constant volume
(b) Constant pressure
 
The magnitudes of the enthalpy changes in these two conditions are different. In first case the volume of the system is kept constant during the course of the measurement by carrying out the reaction in a closed and rigid container and as there is no change in the volume and so no work is also involved.
 
From the first law of thermodynamics we have a relation, <math> \Delta E = Q_v</math>
 
That is, the enthalpy of a reaction at constant volume is equal to the change in the internal energy ('''Δ E''') of the reacting system.
 
The thermal change that occurs in a chemical reaction is only due the difference in the sum of internal energy of the products and the sum of the internal energy of reactants.
 
<math>
\Delta E = \sum E_{products} - \sum E_{reactants}
</math>
 
This also signifies that the amount of heat absorbed at constant volume could be identified with the change in the thermodynamic quantity.
 
At constant pressure, the system is either kept open to the atmosphere or confined within a container on which a constant external pressure is exerted and under these conditions the volume of the system changes.
The thermal change at a constant pressure not only involves the change in the internal energy of the system but also the work performed either in expansion or contraction of the system.
 
<math>
Q_p = \Delta E + W
</math> (work)
 
If ‘W’ is only pressure – volume work, then we have
<math>
Q_p = \Delta H = \Delta E + P \Delta V
</math>
 
<math>
Q_p = \left(\sum E_p - \sum E_r\right) + P \left( V_p - V_r \right)
</math>
 
<math>
Q_p = \left( \sum E_p + P V_p \right) - \left( \sum E_r + P V_r \right)
</math>
 
As enthalpy or heat content is defined by <math>H = E + PV </math>. So we have, <math> Q_p = \sum H_p - \sum H_r = \Delta H</math>
At constant pressure, the heat of the reaction is exactly equal to the enthalpy change, <math>\Delta H</math>, of the reacting system.
 
[[Category:Enthalpy]]
[[Category:Thermochemistry]]
 
[[pl:Standardowe molowe ciepło tworzenia]]

Latest revision as of 05:47, 22 February 2014

Most bars, nightclubs and restaurants have epoxy bar tops. If you cherished this report and you would like to get far more details with regards to resinas epoxi kindly pay a visit to the web site. It is shiny, clear, thick surface, sometimes with some objects inside. Coins, cards and other small item you seen inside clear resin.

What material do they use to build those bar tops and what the process?

Most of the time it is 2 parts chemicals mixed with 1:1 ration. The process is complicated and done by professionals only. Part #1 is epoxy resin and the part #2 is hardener. There are different types of epoxy, based on what you want to accomplish.

Table top resin - main purpose is for table tops, bar tops and any other horizontal surfaces with perfect flat finish. Casting resin/epoxy - used to make molds or building up thickness. If used correctly, may have perfect final surface. Spray Epoxy - this epoxy you can place in spray gun and apply like a lacquer. Sprays in thin layers and grabs pretty quick.

Have you ever seen someone working with epoxy - it is very interesting process.

Area around the bar gets covered with protective film to prevent any spills to get on the floor.

Surfaces get wiped several times with different liquids to completely remove any fat deposits from fingerprints to prevent "fish eye". Process of poring resin on the bar top normally done in several layers. So if you want to place small objects inside epoxy/resin bar top - you can do it between coats.

Resin bar tops are very durable. Surface is hard to scratch and easy to clean. If done correctly it will serve you for 10 years and more.

Can you do it yourself, yes. It is absolutely important to find epoxy supplier who not only work with epoxy but also willing to give you directions on how to work with product and willing to guide you through the process.

Retrieved from "https://en.formulasearchengine.com/index.php?title=Laplace_number&oldid=228740"