ICE and quadratic formula
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 Posts: 105
 Joined: Thu Jul 11, 2019 12:15 am
ICE and quadratic formula
How do you do the calculations for the ICE table without using the quadratic formula?

 Posts: 103
 Joined: Sat Aug 24, 2019 12:16 am
Re: ICE and quadratic formula
You can make your calculations quicker without having to use the quadratic formula when you approximate x. When Ka or Kb is small enough, x can be assumed to be insignificantly small in comparison to the initial concentration of weak acid or base given. As a result, rather than writing out the initial concentration  x in the equation for K, you can just write the initial concentration as is.

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 Joined: Thu Jul 25, 2019 12:16 am
Re: ICE and quadratic formula
The ICE table can be calculated without using the quadratic formula when K is less than 10^3. When K is less than 10^3, one can reason that the change in concentration of the reactant, which has it's new concentration represented in the denominator, is insignificant and cross the x representing this change out. Without this x value in the denominator, the quadratic equation no longer has to be used to solve for x.

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Re: ICE and quadratic formula
For some problems you must use the quadratic formula, there is no way around it. Even when you ignore K you must do the 5% approximation check.

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 Joined: Mon Jan 06, 2020 7:57 am
Re: ICE and quadratic formula
You are able to skip the ICE table when K is less than 10^3. If K is greater than 10^3, you have to use the quadratic formula to solve for x.

 Posts: 107
 Joined: Fri Aug 02, 2019 12:15 am
Re: ICE and quadratic formula
Using the quadratic formula can be skipped if the equilibrium constant is less than 10^3. The value of x would be so small that it would be negligible in the final answer when figuring out the equilibrium concentrations.

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Re: ICE and quadratic formula
you can only avoid using the quadratic formula when you are given a small k value (<10^3), otherwise you would have to solve for x normally, which may require you to use the quadratic formula

 Posts: 103
 Joined: Sat Aug 17, 2019 12:18 am
Re: ICE and quadratic formula
When your K value is smaller than 10^3, you can ignore the minus x in the denominator and use an approximation to determine molar concentration. you can then make sure an approximation is allowed by seeing if your x is less than 5 percent of K.

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 Joined: Wed Sep 18, 2019 12:16 am
Re: ICE and quadratic formula
Abby Soriano 1J wrote:You can make your calculations quicker without having to use the quadratic formula when you approximate x. When Ka or Kb is small enough, x can be assumed to be insignificantly small in comparison to the initial concentration of weak acid or base given. As a result, rather than writing out the initial concentration  x in the equation for K, you can just write the initial concentration as is.
Can you explain this further?

 Posts: 51
 Joined: Wed Feb 20, 2019 12:16 am
Re: ICE and quadratic formula
Emma Joy Schaetz 1E wrote:Abby Soriano 1J wrote:You can make your calculations quicker without having to use the quadratic formula when you approximate x. When Ka or Kb is small enough, x can be assumed to be insignificantly small in comparison to the initial concentration of weak acid or base given. As a result, rather than writing out the initial concentration  x in the equation for K, you can just write the initial concentration as is.
Can you explain this further?
If you have a $1,000,000 and give away $10, you still have relatively $1,000,000. Similarly, if you have an equilibrium constant smaller than k<10^3, it is safe to assume that your resulting equilibrium constant will be more or less the same value. Therefore if you had the equation (4x^2/1.00x), and k<103, the equation could be approximated to (4x^2/1.00) since the value of x is not large enough to cause a significant change.

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 Joined: Thu Jul 11, 2019 12:17 am
 Been upvoted: 1 time
Re: ICE and quadratic formula
The only time you don't have to use the quadratic formula with doing calculations for the Ice table is when K is less than 10^3. Once you plug in your calculations from your Ice table into K the new concentration represented in your denominator, is so insignificant you can cross the x which represents the change out. Without the x value in your denominator, you don't need to use the quadratic equation to solve for x.

 Posts: 111
 Joined: Fri Aug 09, 2019 12:15 am
Re: ICE and quadratic formula
If the initial concentration (such as 0.1x) is small enough, then you can "take away" the x from the bottom ONLY since it is probably a small number, but this is just to make calculations easier. Technically it's not mathematically correct but the difference if you used the quadratic formula is very small.
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