When Ka is small (5% rule)

[305421980]

What was the 5% rule again for when we don't need to use the "-x" in determining final concentrations with an ice table? More specifically what vales should we be comparing to double check for the <5% when Ka is small?

[Paul Hage 2G]

If the value of x is less than 5% of the initial concentration of reactant, then we can approximate. Typically, we can approximate when Ka is less than 10^-3, but the 5% rule is the best way to be sure that approximating will be acceptable.