## 5% Rule

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Jose Robles 1D
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

### 5% Rule

Can someone elaborate what the 5% rule is?

Kate Osborne 1H
Posts: 102
Joined: Fri Aug 30, 2019 12:16 am

### Re: 5% Rule

when using the approximation (removing x when you are subtracting/adding it to something) you must check to make sure that x is less than 5% of the reactant that it is formed from (x will likely be H or OH- so you would use the acid or base)

Jose Robles 1D
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

### Re: 5% Rule

So if it meets the rule, do we just ignore the value?

Brittney Hun 2C
Posts: 104
Joined: Wed Sep 11, 2019 12:15 am

### Re: 5% Rule

You put the concentration you got from approximated the concentrations in the equilibrium values (from an ICE table) over the original concentration that's given and if it is less than 5% the approximation is sound, then if not then you have to use the quadratic formula to find the values.

gabbymaraziti
Posts: 111
Joined: Wed Sep 18, 2019 12:19 am

### Re: 5% Rule

You also know that you can use the approximation if your equilibrium constant, K, is small enough.

JesseAuLec1Dis1G
Posts: 52
Joined: Mon Jun 17, 2019 7:23 am

### Re: 5% Rule

The five percent rule is used in ICE tables. If the x value you get is 5% or less than the initial then you can ignore it. I believe that if the K is 10^-3 or less you can usually make this assumption.