the different Ks

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Funmi Baruwa
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the different Ks

Postby Funmi Baruwa » Fri Jan 15, 2021 11:54 am

I am confused about the different Ks: Ka, Kb, Kw, Kc, and Kp. What exactly are the differences between them?

FionaHunter21
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Re: the different Ks

Postby FionaHunter21 » Fri Jan 15, 2021 11:58 am

They are all the equilibrium constants, but the different subscripts can denote differences in what the equilibrium constant is for. For example, Kw is for water, so the w is for water, Kp is for when there are gases, and their measurements are in pressures, so p=pressure, and Kc is when we are dealing with concentrations, so c=concentrations. They all mean the same thing though, they are all equilibrium constants.

FionaHunter21
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Re: the different Ks

Postby FionaHunter21 » Fri Jan 15, 2021 11:59 am

Likewise, a denotes that it is an acid, and b denotes that it is a base.

Josh Chou 3K
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Re: the different Ks

Postby Josh Chou 3K » Fri Jan 15, 2021 12:04 pm

Ka is the dissociation constant for an acid, which we'll call HA, and is given by the equation Ka = ([A-][H3O+])/[HA]. Similarly, Kb is the dissociation constant for a base, which we'll call BOH, and is given by the equation Kb = ([B+][OH-])/[BOH]. Kw is the dissociation constant for water and always equals 1 x 10-14, and it is the product of Ka x Kb.

Kc is the equilibrium constant of a reaction given the molar concentrations of the products and reactants, and Kpis the equilibrium constant of a reaction given the partial pressures of the products and reactants.

Ephrem Gerald 2A
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Re: the different Ks

Postby Ephrem Gerald 2A » Fri Jan 15, 2021 1:38 pm

K itself when it comes to chemical equilibrium denotes an equilibrium constant. The small letter subscript attached to it just shows you what type of reaction is taking place (sometimes they will give you an equilibrium constant of acid and then you need to solve for the equilibrium constant of the conjugate base, so it is not always denoting the reaction given), or what type of reaction the K value is for. Ka is for an acid, Kb for a base, Kw is the constant for water (which at 25 degrees celsius is 1 x 10^14), Kc when dealing with molar concentrations, and Kp when dealing with partial pressures and gases. Each K is used in a specific setting, but they are all equilibrium constants.

Katie Le 3K
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Re: the different Ks

Postby Katie Le 3K » Fri Jan 15, 2021 3:37 pm

They are all K constants meaning they calculate the same thing (equilibrium constant)
the subscripts denote the type of equilibrium constant it calculates.
Ka, Kb, Kw, Kc, and Kp are K of acid, base, dissociation constant of water, concentration, and partial pressure respectively.

Joshua Swift
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Re: the different Ks

Postby Joshua Swift » Fri Jan 15, 2021 4:59 pm

All K are equilibrium constants and are calculated the same way, but the letters are used to specify which it needed for a certain situation. The a means it is for an acid, b is for a base, c is for concentration, p is for pressure, and w is for water.

Alison Perkins 2B
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Re: the different Ks

Postby Alison Perkins 2B » Fri Jan 15, 2021 5:12 pm

Ka = [H+] [A-] / [HA] -> formula for the acidity constant of equilibrium, where HA is an acid and A- is it's conjugate base
Kb = [BH+] [OH-] / [B] -> formula for the basicity constant of equilibrium, where B is a base and BH is it's conjugate acid
Kw = [H3O+] [OH-] -> this is the formula for equilibrium constant in water autoprotolysis, which at 25C is 1.0 x 10^-14
Kc = [P] / [R] -> this is a general formula for equilibrium constants based on concentration
Kp = [P] / [R] -> this is a general formula for equilibrium constants based on pressures


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