Work1 - as |Work| =p A h = p V where V = V final - V...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Work A common type of work associated by a chemical process is through gas expansion or  compression. An example that you have experienced is the energy produced from the  combustion of gasoline. Gasoline combustion is used to create expanding gases in the  cylinders of your car's engine that push out the pistons. This motion is then translated  into the motion of the car. Let's look at the work associated with moving a piston. Now remember that work is defined as a Force applied over a distance is |Work| = |F ∙  h|, Δ where  h = h Δ final  - h initial . We write the absolute value of work since we still need to make  sure the sign of work agrees with our earlier definitions. Using the definition of p = F/A,  and recognizing A ∙  h Δ  as the change in volume of the cylinder, we can write the work  associated with moving a piston a distance  h
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: as |Work| =p A h = p V where V = V final - V initial . If V is positive then the gas is expanding and doing work on the surroundings. So work should be negative Work = - p V This equation is true in general, not just for pistons. Calculate the work associated with the expansion of a gas from 46 L to 64 L at a constant external pressure of 15 atm. First we calculate V = 64 L - 46 L = 18 L Using P=15 atm, we can then calculate Work = - p V = (15 atm) (18 L) = -270 atm-L Using the conversion between atm-L and Joules of 1 L-atm = 101.325 J Thus, we obtain So, when the gas expands it does 27.4 kJ of work on its surroundings ( i.e. , 27.4 kJ of energy flows out of the system so the work is negative)....
View Full Document

This note was uploaded on 11/22/2011 for the course CHEMISTRY CHM1025 taught by Professor Laurachoudry during the Fall '10 term at Broward College.

Page1 / 2

Work1 - as |Work| =p A h = p V where V = V final - V...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online