K and Kc
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Re: K and Kc
Kc just specifies that you need to use concentrations to find K. If it just says K and the reactants and products are gasses, you use their partial pressures.
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Re: K and Kc
"K" is used to denote Kc or Kp, which you can differentiate by determining if the elements are in a gas phase or an aqueous phase. If the elements are in a gas phase, then you would use the partial pressures to calculate K, which you could also write as Kp. If the elements are in an aqueous phase, then you would use the molar concentrations to calculate K, which you could also write as Kc.
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Re: K and Kc
They are essentially the same thing. If you are given just K, you can usually infer whether to use concentration or partial pressure by what you are given in the problem.
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Re: K and Kc
Do we only use the reaction quotient, Q, when the reaction only goes in the forward direction?
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Re: K and Kc
You can use Q for any reversible reaction that has not reached equilibrium yet. This value of Q can be compared to the value of K to decide whether the forward or the reverse reaction is favored. If Q>K, the reverse reaction is favored, and if Q>K, the forward reaction is favored. Finally if Q=K, the reaction is at equilibrium and the rates of the forward and reverse reactions are equal. Hope this helps.
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Re: K and Kc
When it says Kc, you should be finding the concentrations in molarity. When it says k, if the units are pressure, keep it in pressure. If the units are in molarity, keep it in molarity.
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