Register to reply

Calculating Equilibrium constant

by Malgrif
Tags: constant, equilibrium
Share this thread:
Malgrif
#1
Nov29-08, 09:10 PM
P: 18
1. The problem statement, all variables and given/known data
Consider the system

CO2(g) + H2(g) <====> CO(g) + H2O(g)

Initially, 0.25 mol of water vapour and 0.2 mol of carbon monoxide are placed in a 1.00 L reaction vessel. At equilibrium, spectroscopic evidence shows that 0.1 mol of carbon dioxide is present. Calculate K for the reaction.



2. Relevant equations
equilibrium law


3. The attempt at a solution
So writing down the equilibrium law we get.
Kc = [CO][H2O]/[CO2][H2]

Now we need to find the unknowns. We know 3/4 of the reaction's concentrations but how do you find the forth? An ice table wont work since we don't have a Kc value and without a given H2 value we can't calculate Kc. Stoichometry sounds useless since the system is in equilibrium so what the heck. How do you solve this problem?
Phys.Org News Partner Science news on Phys.org
Security CTO to detail Android Fake ID flaw at Black Hat
Huge waves measured for first time in Arctic Ocean
Mysterious molecules in space
Borek
#2
Nov30-08, 04:16 AM
Admin
Borek's Avatar
P: 23,392
You were already answered somewhere else, but let me repeat: stoichiometry is a key.

Think this way: you start with 25 molecules of water and 20 molecules of carbon monoxide. At equlibrium you find there are 10 molecules of carbon dixode. There were 20 atoms of carbon in the system - if 10 are in the form of dioxide, other 10 must be still in the form of monoxide. That means that 10 molecules of monoxide reacted with water molecules - stoichiometry of the reaction tells you how many molecules of water reacted and how many molecules of hydrogen were produced.


Register to reply

Related Discussions
Equilibrium constant and rate constant Materials & Chemical Engineering 6
Chemistry - calculating equilibrium constant, what am I doing wrong? Biology, Chemistry & Other Homework 6
Calculating equilibrium constant Biology, Chemistry & Other Homework 4
Calculating Moments, Equilibrium Introductory Physics Homework 12
Regarding Equilibrium Constant Biology, Chemistry & Other Homework 2