K and Kc

[Kassandra Molina 2B]

What is the difference between using K and K_c?

[Maeve Gallagher 1J]

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.

[Mika Sonnleitner 1A]

"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.

[Mitch Mologne 1A]

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.

[Miranda 1J]

Do we only use the reaction quotient, Q, when the reaction only goes in the forward direction?

[aTirumalai-1I]

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.

[Phillip Winters 2F]

Kc is just more specific than K, K covers both Kc and Kp

[AtreyiMitra2L]

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.