CH131_4B

# CH131_4B - We can use the ideal gas law for some...

This preview shows pages 1–4. Sign up to view the full content.

We can use the ideal gas law for some quantitative descriptions of chemical reactions involving gas reactants and/or products. For example: consider the thermal decomposition of ammonium nitrite => NH 4 NO 2 (s) N 2 (g) + 2H 2 O(g) (balanced) Suppose 2.55 g of NH 4 NO 2 (s) is heated in a 1.00 L container to 101 o C. What pressure of N 2 (g) is generated in the container? Solution strategy: PV = nRT => P N 2 = n N 2 RT V All known except n N2 Determine n N2 from stoichiometry (1 mol N 2 from 1 mol NH 4 NO 2 ) # mols NH 4 NO 2 = 2.55 g 1 mol NH 4 NO 2 64.0 g = 0.0398 mol NH 4 NO 2 # mols N 2 = 0.0398 mol NH 4 NO 2 1 mol N 2 1 molNH 4 NO 2 = 0.0398 mol N 2

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

View Full Document
P N 2 = n N 2 RT V = 0.0398 mol N 2 0.0821 L atm K - 1 mol ( ) 101+ 273 K ( ) 1.00 L =1.22 atm OK; but for this reaction, for example, 2 gases are formed: NH 4 NO 2 (s) N 2 (g) + 2H 2 O(g) So, what is the total pressure formed from the mixture of these 2 products gases? In the spirit of the ideal gas law (gases are mostly empty space; all intermolecular interactions are neglected) => assume ideal gas law applies to all components in a gas mixture (each gas component ignorant of the presence of the other gases!) Thus for a mixture of m gases we have (note RT/V is a constant): P 1 = n 1 RT V ; P 2 = n 2 RT V ; ...... ; P m = n m RT V ; Total P = P Tot = P 1 + P 2 + .... P m = n 1 + n 2 + .... + n m ( ) RT V P m partial pressure of species m
Total P = P Tot = P 1 + P 2 + .... P m = n 1 + n 2 +.... + n m ( ) RT V P Tot = n Tot RT V where n Tot = n 1 + n 2 + .... + n m ( ) This sentence is called Dalton’s Law: Total P = sum of partial P each gas in a mixture exerts a P as if it were the only component present. P of N

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 04/17/2008 for the course CAS CH131 taught by Professor Zigler during the Spring '08 term at BU.

### Page1 / 16

CH131_4B - We can use the ideal gas law for some...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online