5% Rule


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

5% Rule

Postby Jose Robles 1D » Sat Mar 14, 2020 5:37 pm

Can someone elaborate what the 5% rule is?

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

Re: 5% Rule

Postby Kate Osborne 1H » Sat Mar 14, 2020 5:38 pm

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

Postby Jose Robles 1D » Sat Mar 14, 2020 5:40 pm

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

Postby Brittney Hun 2C » Sat Mar 14, 2020 5:41 pm

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

Postby gabbymaraziti » Sat Mar 14, 2020 5:43 pm

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

Postby JesseAuLec1Dis1G » Sat Mar 14, 2020 5:58 pm

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.

Madelyn Romberg 1H
Posts: 102
Joined: Tue Oct 02, 2018 12:16 am

Re: 5% Rule

Postby Madelyn Romberg 1H » Sat Mar 14, 2020 7:31 pm

Its for simplifying ICE calculations. If the end result is less than 5%, than the approximation is accurate.


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