When to use Quadratic equation

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John_Richey_4A
Posts: 69
Joined: Fri Sep 28, 2018 12:27 am

When to use Quadratic equation

Postby John_Richey_4A » Sun Jan 27, 2019 10:25 pm

When do we have to use the quadratic equation for ice boxes?

404975170
Posts: 68
Joined: Thu Jul 27, 2017 3:00 am

Re: When to use Quadratic equation

Postby 404975170 » Sun Jan 27, 2019 10:45 pm

You use the quadratic equation when u have an x^2 when you set up the equilibrium constant equation. Sometimes you have just an x so you wouldn’t need to do a quadratic you could just solve.

Bryant Vong 2G
Posts: 32
Joined: Fri Apr 06, 2018 11:05 am

Re: When to use Quadratic equation

Postby Bryant Vong 2G » Sun Jan 27, 2019 10:49 pm

You don't use it when you're able to tend x to 0 since the product is lower than 5%.

MadisonFuentes1G
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Joined: Fri Sep 29, 2017 7:04 am

Re: When to use Quadratic equation

Postby MadisonFuentes1G » Sun Jan 27, 2019 10:50 pm

The quadratic formula will naturally end up being used in ICE tables typically when the unknown concentrations for the products in equilibrium are the same and the reactant at equ. has the initial conc. minus the change in conc. This is because, when the K equation is written out with these values, it will look something like (x^2) / (a-x), and when manipulated algebraically to find x, the quadratic equation will have to be used.

Nina Do 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:27 am

Re: When to use Quadratic equation

Postby Nina Do 4L » Wed Jan 30, 2019 7:44 pm

I've been told that we can use the quadratic formula when the value is greater than 10^-3. You can also use the 5% rule to double check if the value is eligible to make x equal to zero and to completely ignore it since it's infinitesimal.

LedaKnowles2E
Posts: 62
Joined: Fri Sep 28, 2018 12:27 am

Re: When to use Quadratic equation

Postby LedaKnowles2E » Thu Jan 31, 2019 4:23 pm

You can use the 5% approximation when K<10^-3 (when the reaction strongly favors the reactants). This means that no quadratic equation solving will be necessary. But if this is not the case and the reaction doesn't strongly favor the reactants, you will end up having to solve a quadratic.

Amar Singh
Posts: 31
Joined: Fri Sep 28, 2018 12:20 am

Re: When to use Quadratic equation

Postby Amar Singh » Sun Feb 03, 2019 2:35 pm

Typically if the problem involves x^2 and Kc < 10^-3, you must use the quadratic equation to solve.

juliasloan_4g
Posts: 67
Joined: Fri Sep 28, 2018 12:28 am

Re: When to use Quadratic equation

Postby juliasloan_4g » Sun Feb 03, 2019 4:46 pm

you need to use the quadratic equation when you can not estimate the x in the denominator and must solve it fully by hand

Tony Chung 2I
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Re: When to use Quadratic equation

Postby Tony Chung 2I » Sat Feb 23, 2019 4:07 pm

You use the quadratic equation when you can't approximate because of how large the K value is. If the K value is greater than 10^-3, then you would have to use the quadratic formula.

Shibhon_Shepard
Posts: 62
Joined: Wed Nov 15, 2017 3:04 am

Re: When to use Quadratic equation

Postby Shibhon_Shepard » Fri Mar 15, 2019 1:28 pm

Does anyone have an example of this either from a book or a review session that goes step by step? thank u

Nghi Nguyen 2L
Posts: 61
Joined: Fri Sep 28, 2018 12:18 am

Re: When to use Quadratic equation

Postby Nghi Nguyen 2L » Fri Mar 15, 2019 9:31 pm

i think Dr. Lavelle says he wants us to always use the quadratic formula and not approximate


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