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Help with Kc calculation!

Really getting frustrated at myself I cannot work this one out. I have the answer given to me by my teacher as 0.19 moldm^-3
Here's the question:

Some phosphorus pentacloride was heated at 250 °C in a sealed container until equilibrium was reached according to the equation:
PCl5 <--> PCl3 + Cl2
Analysis of the mixture showed that it contained
0.0042mol PCl5
0.040mol PCl3
0.040mol Cl2
The total volume was 2dm3.
Calculate Kc

I've tried to do this but come up with a different answer to 0.19
Kc = products/reactants = (0.040/2)(0.040/2) divided by (0.0042/2) = 0.19 :smile:
I really recommend that if you struggle with these calculations watch this (BEST EVER CHEM REVISION):
https://www.youtube.com/watch?v=kkKVY2vl3XM
(edited 5 years ago)
(0.04/2)^2/(0.0042/2) = Bada Bing Bada Boom you get 0.19 (2dp) ^ ^

Original post by Sarah_g_24
Really getting frustrated at myself I cannot work this one out. I have the answer given to me by my teacher as 0.19 moldm^-3
Here's the question:

Some phosphorus pentacloride was heated at 250 °C in a sealed container until equilibrium was reached according to the equation:
PCl5 <--> PCl3 + Cl2
Analysis of the mixture showed that it contained
0.0042mol PCl5
0.040mol PCl3
0.040mol Cl2
The total volume was 2dm3.
Calculate Kc

I've tried to do this but come up with a different answer to 0.19
Reply 3
Avatar for Sarah_g_24
Sarah_g_24
OP
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Original post by MH1234567
Kc = products/reactants = (0.040/2)(0.040/2) divided by (0.0042/2) = 0.19 :smile:
I really recommend that if you struggle with these calculations watch this (BEST EVER CHEM REVISION):
https://www.youtube.com/watch?v=kkKVY2vl3XM


Oh my gosh I feel so stupid! tysm!
I was doing reactants over products LOL

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