5% approximating equilibrium concentration

[406003397]

When dealing with numbers in this situation, they are often quite precise and either smaller than or larger than conventional conception. Having this in mind, why is there the need to have such a value as 5%, when values can often not be assumed?

[Tasnim Jahan 2K]

The 5% approximation is used to simplify calculations, and it is used when the change in concentration of a reactant or product is less than 5% of its initial concentration. The approximation is used because it is assumed that the change in concentration is negligible and will not impact the overall equilibrium in general.

[Callista OConnor]

Adding onto the above response, this rule is typically used when calculating a reaction quotient where there is a very small change from initial [ ] to final [ ] . For example, when you set up your ICE table and you find you have a very small "x", your equation may look like

K = x^2/[ ]initial -x

and if x is very small, it won't make much of a difference in the denominator to include it and solving with the quadratic formula will be more of a hassle than you need.