 # A Level Chemistry Tutorial 2019: Ideal Gas Law In Combustion Engine Analysis

hello everyone I am mr. Tong and you are watching chemistry tutorial let's get into it this question is testing us on the topic the gaseous thing the Pistons in an auto mobile energy and driven by the following reaction which takes place in the cylinder Lumos of octane reacts with 25 moles of oxygen to produce 16 moles of carbon dioxide and 80 moles of water if the cylinder has a total volume of six point one five meters and one-fifth of the air filling the cylinder at 1 atm and 27 degree Celsius is oxygen calculate the partial pressure of oxygen in the engine and hence determine the mass of obtain necessary to combine exactly with oxygen pick on the Monegasque constant s 8.314 joules per kelvin per mole we solve this question we need to make use of the I do gas law PV equals to NRT the P represents pressure in Pasco V represents the volume in meter cube and represents the number of moles of gas is a Monegasque constant which is given as a point tree unfold joules per Kelvin per mole ah is our temperature and it has to be expressed as Kelvin since the volume is fixed at 6.15 liters a semana gas constant and the temperature is fixed at 27 degree Celsius therefore we can get this expression where our pressure is directly proportional to the number of moles of gas from an equation where the partial pressure of oxygen over to the pressure is equals to the number of moles of oxygen over the total number of moles of gas so partial pressure of oxygen over 1 ATM which is given in the question is equals to 1/5 solve for the partial pressure of oxygen in turns out that the partial pressure of oxygen is equals to 0.2 atm yes we are total make use of this results to determine the mass of octane because there is a word called hence once again we need to make use of the I you gas law PV equals NRT for oxygen gas pressure is equals to 0.2 ATM which you obtain for the previous part but the pressure has to be in pasca so we multiply zero point 2 by 1 0 1 3 2 5 all it was given impressionists 6.15 beta and 6.15 liter has to be converted to meter cube so we multiply this by 10 to the power minus 3 and represents the number of moles of oxygen gas ah is given as a point to inform temperature is 27 degree Celsius but he has to express as Kelvin so we add 273 to it solve for the number moles of oxygen and we'll get an answer s zero point zero four nine nine six seven moles now if you don't get the equation the stock matter equation the number of moles are obtained to a number of moles of oxygen is equal to 2 is 225 since we already know that double moles of oxygen we can find the number of moles of pain by multiplying this value by 2 over 25 and hence the number of moles of a pain is equals to zero point zero three nine nine seven four notes we want to leave our answer our final ancestry as F therefore I'm using 5 X 5 SF to maintain the accuracy of the data if you know the number of moles on paint we can find the mass of a pain simply by multiplying the double balls by the molar mass which is 114 and we our answer is zero point four five six grams corrected to three SF that's it for now if you like this video subscribe and hit the notification button so they don't miss any of my future chemistry videos or visit our website at www.flcfs.org calm talk to you in the next one is our

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