5% rule

[Alexis Robles 2k]

What is the 5% rule and when do we apply it? Thanks.

[Bryce Ramirez 1J]

The five percent rule is when you are checking to see if your approximation for the equilibrium constant is valid. You apply it by taking the equilibrium concentration and dividing by the initial concentration and multiplying by 100. If less than five percent, then your approximation is valid. But if it is greater than five percent, then then something is wrong with your approximation.

[205007651]

To calculate it you just do (equilibrium concentration/initial concentration) * 100. It is valid if it's less than 5%.
If you get around 5% professor Lavelle said it might be due to approximation during calculations so you should try to do them again.

[Chantel_2I]

When we create ICE charts and and solve for X, we often get in the denominator the initial concentration minus X. However, we use the 5% rule to determine whether it is valid to simply the denominator to simply the initial concentration to make it easier to solve for X. We can do this simplification when X is less than 5% of the initial concentration.

[Nicholas Chin 1G]

This rule is also only applied if K is a small value (<10^-3).