1.3.2 Moles and gases

Ideal gas law

Make sure you use the appropriate pair of PV units (Eg. kPa must be with dm³) and always use Kevin for temperature.
K = ^oC + 273   Eg. 0^oC is 273K

2 assumptions that are NOT true when dealing with real gas (instead of ideal gas):

when describing an ideal gas with kinetic theory we assumes this but it is not true for real gases at high temperature and pressure

• The volume of the gas particles is negligible

*At low pressure this is negligible but at high pressure is can be about 20% of the total volume

• The are no attractive forces between the particles

*at low pressure the particles are so widely spaced that interactive forces are highly unlikely but increases at higher pressures

*low temperatures slow particle movement and so increase interactive forces

1. At STP (standard temperature and pressure), what is the volume of 1 mole of gas?

Don't memorize this, use the data booklet. The molar volume is 22.7 dm³.

2. For reaction with gases, ratio can be done using the volume

Example

Nitrogen gas (N₂) can be prepared from this reaction:

2NH₃ + 3CuO → N₂ + 3Cu + 3H₂O

If 18.1L  NH₃ are reacted with 90.40 g CuO, determine the volume of N₂ that can be formed at STP.

A bit of history should you interested in which scientist figured out which part of the ideal gas equation...