Dalton's+PP

 **Dalton's Law of Partial Pressures** In teh teams own words...teh pressures of two ideal gases under teh same conditions are added together to solve for teh total pressure.



 PressureTotal = Pressure1 + Pressure2 ... Pressuren
 Dalton's Law explains that the total pressure is equal to the sum of all of the pressures of the parts. This only is absolutely true for ideal gases, but the error is small for real gases. This may at first seem a trivial law, but it can be very valuable in the chemistry lab. Another important contribution by John Dalton was his generalization that all gases expand equally on going to the same higher temperature.  

 Dalton's Law of Partial Pressures Pa + Pb Ptotal = Pa+Pb Inifinite amount of gases. More gases, the more pressure. Two pressures just add together.

Consider a case in which two gases, A and B, are in a container of volume V. Pa = naRT/V na is the number of moles of A. Pb = nbRT/V nb is the number of moles of B. Pt = Pa + Pb Xa = na/na+nb xb = nb/na+nb Xa = % composition. Na + Nb = total moles. Pa = XaPt Pb = XbPt Pi=XiPi i stands for any gas.

A sample of natural gas contains 8.24 moles of CH4, 0.421 moles of C2H8 and 0.116 moles of C3H8. If the total pressure of the gases is 1.37 atm, what is the partial pressure of propane (C3H8)? Pi=XiPt Pt = 1.37 atm Xpropane = 0.116/8.24+0.421+0.116=0.0132 Ppropane = 0.0132 x 1.37 atm = 0.0181 atm [Taken from Mary Smith's Wikispace - www.rlhonorschem3.wikispaces.com/mary]

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media type="custom" key="3653985" the total pressure exerted by them is equal to the sum of their partial pressure".** || || || In terms of KINETIC MOLECULAR THEORY, Dalton's law of partial pressure can be explained as: || The total pressure exerted by the gaseous mixture is equal to the sum of collisions of the molecules of individual gas ."** || moles are **n**t. || P = nRT/V || || || **OR** ||
 * |||| **PARTIAL PRESSURE ** || http://www.citycollegiate.com/daltons_lawXI.htm ||
 * ^  |||||| In a mixture of different gases which do not react chemically each gas behaves independently of the other gases and exerts its own pressure. This individual pressure that a gas exerts in a mixture of gases is called it's partial pressure. ||
 * ^  |||| DALTON'S LAW OF PARTIAL PRESSURE ||   ||
 * |||||| Based on this behaviour of gases, JOHN DALTON formulated a basic law which is known as "The Dalton's law of partial pressure" . ||
 * ||  |||||| The law states that: ||
 * |||||| **"If two or more gases** (which do not react with each other) **are enclosed in a vessel,
 * |||| **MATHEMATICAL REPRESENTATION ** ||  ||
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Consider a mixture of three non-reacting gases **a**, **b** <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">and **c** .<span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Partial pressures of these gases are **P**a ,**P**b and **P**c .According to Dalton's law of partial pressure, their total pressure is given by:
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">**P**total = **P**a + **P**b + **P**c
 * ^  |||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">**DALTON'S LAW IN THE LIGHT OF KINETIC MOLECULAR THEORY** ||   ||
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">According to kinetic molecular theory of gases there is no force of attraction or repulsion among the gas molecules. Thus each gas behaves independently in a mixture and exerts it's own pressure.
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">**"In a non-reacting mixture of gases, each gas exerts separate pressure on the container in which it is confined due to collision of it's molecules with the walls of container.
 * ^  |||| **<span style="font-family: Verdana,Arial,Helvetica,sans-serif;">EXPRESSION FOR PARTIAL PRESSURE ** ||   ||
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Consider a gaseous mixture of three different gases **a**, **b** and **c** enclosed in a container of volume **V**dm3 at **T** Kelvin. Let the partial pressures of these gases are <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">**P**a ,**P**b and **P**c respectively and total pressure of mixture is **P**t . Let there are <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">**n**a ,**n**b and **n**c moles of each gas respectively and the total number of
 * ^  |||||| <span style="display: block; text-align: left; font-family: Verdana,Arial,Helvetica,sans-serif;">Three gases confined in a cylinder under similar conditions:[[image:http://www.citycollegiate.com/partial_pressure1.gif width="113" height="127" align="absmiddle"]] ||
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Using equation of state of gas: ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">PV = nRT
 * OR**
 * ^  || <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">For gas **a** ||   ||   ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pa = naRT/V--- (i) ||
 * ^  || <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">For gas **b** ||   ||   ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pb = naRT/V--- (ii) ||
 * ^  || <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">For gas **c** ||   ||   ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pc = ncRT<span style="font-family: Verdana,Arial,Helvetica,sans-serif;">/V --- (iii) ||
 * ^  || <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">For any gas ||   ||   ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pgas = ngasRT<span style="font-family: Verdana,Arial,Helvetica,sans-serif;">/V
 * OR**
 * ^  |||||| [[image:http://www.citycollegiate.com/partial_pressure2.gif width="97" height="53" align="absmiddle"]]<span style="font-family: Verdana,Arial,Helvetica,sans-serif;">-(a)
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Adding equation (i), (ii) and (iii), we get, ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pt = naRT/V + nbRT/V + ncRT/V ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pt = (na + nb + nc)RT/V
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">But nt = na + nb + nc ||
 * ^  |||||| <span style="display: block; text-align: center; font-family: Verdana,Arial,Helvetica,sans-serif;">Pt = nt RT/V ||
 * ^  |||||| [[image:http://www.citycollegiate.com/partial_pressure3.gif width="168" height="48"]] ||
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Comparing equation (a) and (b), we get, ||
 * ^  |||||| [[image:http://www.citycollegiate.com/partial_pressure4.gif width="107" height="149"]] ||
 * ^  |||||| <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">This expression indicates that the pressure of a gas is proportional to number of moles if confined under similar conditions. ||