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The equilibrium constant ... confused :( !
Phosphorus (V) chloride disassociates at high temperatures according to the equation
PCl5 (reversible reaction sign) PCl3 + Cl2
(all in gas state)
83.4 grams of PCl5 are placed in a vessel of volume 9.23 dm3. At equilibrium at a certain temperature, 11.1 grams of chlorine are produced at a total pressure of 250 kPa.
a) Calculate the number of moles of each of the gases in the vessel at equilibrium.
I guess this is where my problem lies. I've not had a question structured quite like this, they have all given me the initial mol and then the mols at equilibrium to begin with ...
I can only think to use Moles = Mass / Mr, and have got the following ...
Moles of PCl5 = 0.40
Moles of PCl3 = 0.53
Moles of Cl2 = 0.16
I'm really confused however, about whether these are correct ... I know ive been told the mass of the PCl5 and the Cl2, and so used these as given ... for the PCl3 however, i found the difference in mass (83.4 - 11.1) and used this value for the moles calculation. Is this correct?
b) Write an expression for the equilibrium constant, Kc, for the above reaction
I think i've got this okay
c) Calculate the value of the equilibrium constant, Kc, for the above equilibrium.
I know I have to use the concentrations of the different substances at equilibrium and substitute these into the calculation, but am confused as to how to obtain the concentrations ... do i simply use concentration = moles / volume ... with the volume being 9.23 and the moles being the values worked out in part a?
Any clarifications would be really helpful and appreciated
PCl5 (reversible reaction sign) PCl3 + Cl2
(all in gas state)
83.4 grams of PCl5 are placed in a vessel of volume 9.23 dm3. At equilibrium at a certain temperature, 11.1 grams of chlorine are produced at a total pressure of 250 kPa.
a) Calculate the number of moles of each of the gases in the vessel at equilibrium.
I guess this is where my problem lies. I've not had a question structured quite like this, they have all given me the initial mol and then the mols at equilibrium to begin with ...
I can only think to use Moles = Mass / Mr, and have got the following ...
Moles of PCl5 = 0.40
Moles of PCl3 = 0.53
Moles of Cl2 = 0.16
I'm really confused however, about whether these are correct ... I know ive been told the mass of the PCl5 and the Cl2, and so used these as given ... for the PCl3 however, i found the difference in mass (83.4 - 11.1) and used this value for the moles calculation. Is this correct?
b) Write an expression for the equilibrium constant, Kc, for the above reaction
I think i've got this okay
c) Calculate the value of the equilibrium constant, Kc, for the above equilibrium.
I know I have to use the concentrations of the different substances at equilibrium and substitute these into the calculation, but am confused as to how to obtain the concentrations ... do i simply use concentration = moles / volume ... with the volume being 9.23 and the moles being the values worked out in part a?
Any clarifications would be really helpful and appreciated
the mols for PCl3 and Cl2 are the same, but you've got them different. see if that helps
c) Calculate the value of the equilibrium constant, Kc, for the above equilibrium.
I know I have to use the concentrations of the different substances at equilibrium and substitute these into the calculation, but am confused as to how to obtain the concentrations ... do i simply use concentration = moles / volume ... with the volume being 9.23 and the moles being the values worked out in part a?
always do mols/volume, so in your case 9.23 would be correct.
I know I have to use the concentrations of the different substances at equilibrium and substitute these into the calculation, but am confused as to how to obtain the concentrations ... do i simply use concentration = moles / volume ... with the volume being 9.23 and the moles being the values worked out in part a?
always do mols/volume, so in your case 9.23 would be correct.
darth_vader05
the mols for PCl3 and Cl2 are the same, but you've got them different. see if that helps
Mm-hmm, that does help. I wasn't sure if i was supposed to try to find the mass of the PCl3 by assuming that the total mass of the reactant would equal the total mass of the products and then using this to calculate the moles. So, i just calculate the moles for the PCl5 and the Cl and then use the same Cl value for the PCl3 because they are at equilibrium?
h1nna
Mm-hmm, that does help. I wasn't sure if i was supposed to try to find the mass of the PCl3 by assuming that the total mass of the reactant would equal the total mass of the products and then using this to calculate the moles. So, i just calculate the moles for the PCl5 and the Cl and then use the same Cl value for the PCl3 because they are at equilibrium?
i think so!! i'm not good at explaining things
i think it's because its a one to one reaction. 1 mole pl5 gives one mol of cl and plc3.
h1nna
That kind of makes sense ... seems similar to other past examples ive done too ... thankyou for your help x
no problem
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