When to use K and Kp
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When to use K and Kp
When you are given a random chemical equation, does it matter if you use K or Kp (concentration or pressure) if the question doesn't specifically state what it wants?
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Re: When to use K and Kp
If it doesn't specify Kc or Kp, either should be fine. However, you should be able to tell what the question wants based on what's given. For example, if it gives you concentration values, you would probably have to find Kc.
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Re: When to use K and Kp
Typically, if the problem gives concentration, then Kc is used. In most cases, it will be easy to know what you are asked for, if not specified.
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Re: When to use K and Kp
Kristina Rizo 2K wrote:I thought Kp was used for gas only? Can someone clarify this please.
Kp is used for gases to determine partial pressures! Kc is used for concentrations and Ka and Kb are for acids and bases.
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Re: When to use K and Kp
Kallista McCarty 1C wrote:Kristina Rizo 2K wrote:I thought Kp was used for gas only? Can someone clarify this please.
Kp is used for gases to determine partial pressures! Kc is used for concentrations and Ka and Kb are for acids and bases.
This might be a dumb question but you calculate all of these the same way right, with products/reactants?
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Re: When to use K and Kp
If the problem doesn't specify, either should be fine to use. Although, if you are given concentrations then you are likely to use Kc rather than Kp, or if the problem mentions a gas, you would use Kp for partial pressure
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Re: When to use K and Kp
In a peer review session, the UA suggested that we should use Kc unless it specifically tells us to find Kp or gives information using atm or bars.
Re: When to use K and Kp
And another thing to look out for, even if the question doesn't specify whether or not it wants Kc or Kp look at the given equation. If the reactants and products have "(g)" next to them, you'll look to find Kp because they're gases and you would use the partial pressures for it.
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Re: When to use K and Kp
Maya Pakulski 1D wrote: This might be a dumb question but you calculate all of these the same way right, with products/reactants?
Yes, although you might have to do some other calculations to get everything in the same units.
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Re: When to use K and Kp
Typically it will specify. When given all gases, you will likely use partial pressure. If they specify concentration when given gasses, you may need to use PV=nRT to convert between the two. K is a general symbol which can apply to Kp or Kc. In this class he has had us specify which we are using.
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Re: When to use K and Kp
What if you are given all gases, can you still use Kc? I know you can convert to Kp but why wouldn't we just use concentrations if they are given?
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Re: When to use K and Kp
I was told that Kp can be used for gases and Kc can be used for aqueous solutions. I believe that Kc can be used for gases as well if given concentrations but I am also unsure about that.
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