Writing Equilibrium Constant Labels

Moderators: Chem_Mod, Chem_Admin

Bryce Ramirez 1J
Posts: 120
Joined: Sat Aug 24, 2019 12:16 am

Writing Equilibrium Constant Labels

Postby Bryce Ramirez 1J » Mon Jan 06, 2020 5:41 pm

When writing the products and reactants for the equilibrium constant, why do we add P before the formula that is part of the chemical equation? Does this represent the partial pressure?

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

Re: Writing Equilibrium Constant Labels

Postby sarahforman_Dis2I » Mon Jan 06, 2020 5:45 pm

Bryce Ramirez 1J wrote:When writing the products and reactants for the equilibrium constant, why do we add P before the formula that is part of the chemical equation? Does this represent the partial pressure?


I believe that you are correct. If all of the substances in the equilibrium reaction are in the gas phase, that means that to determine when the system is at equilibrium we will use P, the partial pressure to calculate K. If the products and reactants are all in an aqueous solution, then concentration (the estimate for activity) would be used in the equilibrium expression.

Megan Vu 1J
Posts: 101
Joined: Thu Jul 25, 2019 12:15 am

Re: Writing Equilibrium Constant Labels

Postby Megan Vu 1J » Mon Jan 06, 2020 5:56 pm

P does means partial pressure because you are using a gas throughout the entire equilibrium. The equilibrium constant would also be denoted as Kp. You can often use the equation, PV = nRT in order to get the concentration of the whole equilibrium if you were asked to find it.

Both Kp and Hc have the same system where products are over reactants in a ratio.

Amy Pham 1D
Posts: 103
Joined: Fri Aug 09, 2019 12:15 am

Re: Writing Equilibrium Constant Labels

Postby Amy Pham 1D » Mon Jan 06, 2020 5:57 pm

Little clarification, even when all the products and reactants are given in the gas phase you don't always have to use partial pressures to calculate the K value. If you are given concentrations, then using those and calculating K_c is fine as well.

Tiffany_Chen 2K
Posts: 106
Joined: Fri Aug 30, 2019 12:15 am

Re: Writing Equilibrium Constant Labels

Postby Tiffany_Chen 2K » Mon Jan 06, 2020 6:24 pm

Kc is used for concentrations (M), which can be gases or aqueous molecules, Kp uses partial pressures of gases. Question should be clear on which one to use.


Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 1 guest