Gases & Moles !

For example: The volume of a balloon occupied by a certain gas, depends on the temprature and pressure.

When doing your homework, you'll need to know the following things:

- STP (Standard Temprature & Pressure)
* 273 K / O degrees celcius and 101.3 KPa

- SATP (Standard Ambient Temperature & Pressure)
* 298 K / 25 degrees celcius and 100 KPa

Note: For most of homework and tests we'll only (usually) take STP into consideration, but it is also helpful to know the SATP.

Now, to find the volume occupied by gases, or the number of moles in a gas.. We must..

Know: That the volume of 1 mole of ANY GAS at STP, is 22.4 L
- Molar Volume at STP = 22.4 L

When you want to find your VOLUME, you use: 22.4 L/1 mol (22.4 L over 1 mole)
When you want to find your # of MOLES, you use: 1 mol/22.4L (1 mole over 22.4 L)

When you want to get rid of that "unit", you multiply it with that same unit in the DENOMINATOR.

Btw, it doesn't really matter WHAT your gas is, 'cause you don't really need to know, it's pretty much irrelevant.

Get it get it? :) So now.. LET'S DO SOME EXAMPLES! YAAAAY!

1) Find the volume occupied by 0.060 Mol of carbon dioxide gas at STP
0.060 mol x 22.4 L/mol = 1.34 L
(notice how you start off with moles, and the "Thing" your multiplying it by has moles also in the denominator)

2) Find the number of moles in a 264.0 mL sample of NO2 at O degrees celcius and 101.3 KPa (STP)
264 mL x 1 L/1000 mL = 0.264 L
(you must first convert millilitres to litres) then..
0.264 L x 1 mol/22.4L = 0.012 mol

3) Find the Volume occupied by 22.0 g of carbon dioxide gas (CO2) at STP
(you must first find the molar mass of the carbon dioxide gas), which is 44 g
then.. 22g x 1 mol/ 44 g x 22.4 L/1 mol = 11.2
(because the unit of molar mass is g/mol, you can reciprocal it and turn it into 1 mol/44g, and the answer to that will be in MOLES, (b/c the g cancel out) and you can multiply it by your STP litres for volume!)

HOMEWORK:
- Sheet (Unit 2 Homework Sheet)
* #5 - 10 ALL.

(Queen's post!)

Watch this video on converting litres and moles and stuff :)
http://www.youtube.com/watch?v=AHqNiEwcXiE